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Theodore R Cummins - One of the best experts on this subject based on the ideXlab platform.
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inhibition of navβ4 peptide mediated resurgent sodium currents in nav1 7 channels by carbamazepine riluzole and anandamide
Molecular Pharmacology, 2011Co-Authors: Jonathan W Theile, Theodore R CumminsAbstract:Paroxysmal extreme pain disorder (PEPD) and inherited erythromelalgia (IEM) are inherited pain syndromes arising from different sets of gain-of-function mutations in the sensory neuronal sodium channel isoform Nav1.7. Mutations associated with PEPD, but not IEM, result in destabilized inactivation of Nav1.7 and enhanced resurgent sodium currents. Resurgent currents arise after relief of ultra-fast open-channel block mediated by an endogenous blocking particle and are thought to influence neuronal excitability. As such, enhancement of resurgent currents may constitute a pathological mechanism contributing to sensory neuron hyperexcitability and pain hypersensitivity associated with PEPD. Furthermore, pain associated with PEPD, but not IEM, is alleviated by the sodium channel inhibitor carbamazepine. We speculated that selective attenuation of PEPD-enhanced resurgent currents might contribute to this therapeutic effect. Here we examined whether carbamazepine and two other sodium channel inhibitors, riluzole and anandamide, exhibit differential inhibition of resurgent currents. To gain further insight into the potential mechanism(s) of resurgent currents, we examined whether these inhibitors produced correlative changes in other properties of sodium channel inactivation. Using stably transfected human embryonic kidney 293 cells expressing wild-type Nav1.7 and the PEPD mutants T1464I and M1627K, we examined the effects of the three drugs on Navβ4 peptide-mediated resurgent currents. We observed a correlation between resurgent current inhibition and a drug-mediated increase in the rate of inactivation and inhibition of persistent sodium currents. Furthermore, although carbamazepine did not selectively target resurgent currents, anandamide strongly inhibited resurgent currents with minimal effects on the peak transient current amplitude, demonstrating that resurgent currents can be selectively targeted.
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nav1 7 mutations associated with paroxysmal extreme pain disorder but not erythromelalgia enhance navβ4 peptide mediated resurgent sodium currents
The Journal of Physiology, 2011Co-Authors: Jonathan W Theile, Brian W Jarecki, Andrew D Piekarz, Theodore R CumminsAbstract:Inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD) are inherited pain syndromes predominantly caused by missense mutations in the peripheral neuronal voltage-gated sodium channel (Nav) isoform Nav1.7. While both IEM and PEPD mutations increase neuronal excitability, IEM mutations primarily enhance activation and PEPD mutations impair inactivation. In addition, one PEPD mutation, Nav1.7-I1461T, has been shown to increase resurgent sodium currents in dorsal root ganglion (DRG) neurons. Because resurgent currents have been implicated in increased neuronal excitability, we asked whether (1) additional PEPD mutations located within the putative inactivation gate and docking sites and (2) IEM mutations might also increase these unusual currents. Resurgent currents are generated following open-channel block at positive potentials by an endogenous blocking particle and subsequent expulsion of this blocker upon repolarization to moderately negative potentials. Here we used a mimetic of the putative blocking particle, the Navβ4 peptide, to determine if enhanced resurgent currents are induced by three distinct PEPD mutations and two IEM mutations in stably transfected HEK293 cells. We demonstrate that (1) Nav1.7-mediated resurgent currents are observed in HEK293 cells with the Navβ4 peptide in the recording pipette, (2) while the PEPD mutants M1627K, T1464I and V1299F exhibit enhanced resurgent current amplitudes compared to wild-type, the IEM mutants I848T and L858H do not, and (3) there is a strong correlation between the decay time constant of open-channel fast inactivation and resurgent current amplitude. These data suggest that resurgent currents may play a role in the neuronal hyperexcitability associated with PEPD, but not IEM, mutations.
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nav1 7 mutations associated with paroxysmal extreme pain disorder but not erythromelalgia enhance navβ4 peptide mediated resurgent sodium currents
The Journal of Physiology, 2011Co-Authors: Jonathan W Theile, Brian W Jarecki, Andrew D Piekarz, Theodore R CumminsAbstract:Abnormal pain sensitivity associated with inherited and acquired pain disorders occurs through increased excitability of peripheral sensory neurons in part due to changes in the properties of voltage-gated sodium channels (Navs). Resurgent sodium currents (I(NaR)) are atypical currents believed to be associated with increased excitability of neurons and may have implications in pain. Mutations in Nav1.7 (peripheral Nav isoform) associated with two genetic pain disorders, inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD), enhance Nav1.7 function via distinct mechanisms. We show that changes in Nav1.7 function due to mutations associated with PEPD, but not IEM, are important in I(NaR) generation, suggesting that I(NaR) may play a role in pain associated with PEPD. This knowledge provides us with a better understanding of the mechanism of I(NaR) generation and may lead to the development of specialized treatment for pain disorders associated with I(NaR).
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alternative splicing of na v 1 7 exon 5 increases the impact of the painful PEPD mutant channel i1461t
Channels, 2009Co-Authors: Brian W Jarecki, Patrick L Sheets, James O Jackson, Yucheng Xiao, Theodore R CumminsAbstract:Alternative splicing is known to alter pharmacological sensitivities, kinetics, channel distribution under pathological conditions, and developmental regulation of VGSCs. Mutations that alter channel properties in Na(V)1.7 have been genetically implicated in patients with bouts of extreme pain classified as inherited erythromelalgia (IEM) or paroxysmal extreme pain disorder (PEPD). Furthermore, patients with IEM or PEPD report differential age onsets. A recent study reported that alternative splicing of Na(V)1.7 exon 5 affects ramp current properties. Since IEM and PEPD mutations also alter Na(V)1.7 ramp current properties we speculated that alternative splicing might impact the functional consequences of IEM or PEPD mutations. We compared the effects alternative splicing has on the biophysical properties of Na(V)1.7 wild-type, IEM (I136V) and PEPD (I1461T) channels. Our major findings demonstrate that although the 5A splice variant of the IEM channel had no functional impact, the 5A splice variant of the PEPD channel significantly hyperpolarized the activation curve, slowed deactivation and closed-state inactivation, shifted the ramp current activation to more hyperpolarized potentials, and increased ramp current amplitude. We hypothesize a D1/S3-S4 charged residue difference between the 5N (Asn) and the 5A (Asp) variants within the coding region of exon 5 may contribute to shifts in channel activation and deactivation. Taken together, the additive effects observed on ramp currents from exon 5 splicing and the PEPD mutation (I1461T) are likely to impact the disease phenotype and may offer insight into how alternative splicing may affect specific intramolecular interactions critical for voltage-dependent gating.
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impact of nav1 7 PEPD missense mutations that slow the rate of inactivation on sensory neuronal resurgent sodium currents
Biophysical Journal, 2009Co-Authors: Brian W Jarecki, James O Jackson, Andrew D Piekarz, Theodore R CumminsAbstract:Voltage-gated sodium (Nav1.1-9) channels are dynamic transmembrane proteins that, in response to changes in the potential across the lipophilic cell membrane, undergo specific conformational (gating) modifications, between ion-conducting (open) and non-conducting (closed and inactivated) states, to selectively conduct sodium ions through their aqueous pore. Importantly, changes in these voltage-dependent gating properties can impact action potential (AP) characteristics. TTX-sensitive sodium channels in cerebellar neurons can produce resurgent currents (Raman & Bean, 1997), intriguing currents that are re-activated during intermediate repolarizations following strong, but short, depolarizations. We observe resurgent currents in some DRG neurons and found that wild-type Nav1.6 but not wild-type Nav1.7 channels can generate resurgent currents in DRG neurons (Cummins et al., 2005). It has been demonstrated that, in cerebellar neurons from Nav1.6-null mice, slowing inactivation of the remaining Nav current can induce resurgent currents (Grieco & Raman, 2004). Interestingly, single-point missense mutations in the SCN9A gene that encode for Nav1.7, implicated in paroxysmal extreme pain disorder (PEPD), slow the rate of Nav1.7 inactivation (Jarecki et al., 2008). Therefore, we hypothesized that slowing of Nav1.7 by PEPD mutations might induce abnormal resurgent currents, thus altering AP properties. To explore this hypothesis, we transiently transfected adult rat DRG neurons with a TTX-resistant form of human Nav1.7-wild-type or PEPD mutant cDNA and rat Nav1.8-targeted shRNA. Voltage-dependent properties were observed using whole-cell voltage-clamp electrophysiology and AP generation was tested using current-clamp electrophysiology. Recordings were made in the presence and absence of extracellular TTX. These experiments should yield insight into (1) the mechanism of resurgent sodium current generation in DRG neurons, (2) a potential additive effect in channel dysfunction observed in PEPD, and (3) how these mutant channels contribute to alterations in AP characteristics.
Brian W Jarecki - One of the best experts on this subject based on the ideXlab platform.
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nav1 7 mutations associated with paroxysmal extreme pain disorder but not erythromelalgia enhance navβ4 peptide mediated resurgent sodium currents
The Journal of Physiology, 2011Co-Authors: Jonathan W Theile, Brian W Jarecki, Andrew D Piekarz, Theodore R CumminsAbstract:Inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD) are inherited pain syndromes predominantly caused by missense mutations in the peripheral neuronal voltage-gated sodium channel (Nav) isoform Nav1.7. While both IEM and PEPD mutations increase neuronal excitability, IEM mutations primarily enhance activation and PEPD mutations impair inactivation. In addition, one PEPD mutation, Nav1.7-I1461T, has been shown to increase resurgent sodium currents in dorsal root ganglion (DRG) neurons. Because resurgent currents have been implicated in increased neuronal excitability, we asked whether (1) additional PEPD mutations located within the putative inactivation gate and docking sites and (2) IEM mutations might also increase these unusual currents. Resurgent currents are generated following open-channel block at positive potentials by an endogenous blocking particle and subsequent expulsion of this blocker upon repolarization to moderately negative potentials. Here we used a mimetic of the putative blocking particle, the Navβ4 peptide, to determine if enhanced resurgent currents are induced by three distinct PEPD mutations and two IEM mutations in stably transfected HEK293 cells. We demonstrate that (1) Nav1.7-mediated resurgent currents are observed in HEK293 cells with the Navβ4 peptide in the recording pipette, (2) while the PEPD mutants M1627K, T1464I and V1299F exhibit enhanced resurgent current amplitudes compared to wild-type, the IEM mutants I848T and L858H do not, and (3) there is a strong correlation between the decay time constant of open-channel fast inactivation and resurgent current amplitude. These data suggest that resurgent currents may play a role in the neuronal hyperexcitability associated with PEPD, but not IEM, mutations.
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nav1 7 mutations associated with paroxysmal extreme pain disorder but not erythromelalgia enhance navβ4 peptide mediated resurgent sodium currents
The Journal of Physiology, 2011Co-Authors: Jonathan W Theile, Brian W Jarecki, Andrew D Piekarz, Theodore R CumminsAbstract:Abnormal pain sensitivity associated with inherited and acquired pain disorders occurs through increased excitability of peripheral sensory neurons in part due to changes in the properties of voltage-gated sodium channels (Navs). Resurgent sodium currents (I(NaR)) are atypical currents believed to be associated with increased excitability of neurons and may have implications in pain. Mutations in Nav1.7 (peripheral Nav isoform) associated with two genetic pain disorders, inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD), enhance Nav1.7 function via distinct mechanisms. We show that changes in Nav1.7 function due to mutations associated with PEPD, but not IEM, are important in I(NaR) generation, suggesting that I(NaR) may play a role in pain associated with PEPD. This knowledge provides us with a better understanding of the mechanism of I(NaR) generation and may lead to the development of specialized treatment for pain disorders associated with I(NaR).
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alternative splicing of na v 1 7 exon 5 increases the impact of the painful PEPD mutant channel i1461t
Channels, 2009Co-Authors: Brian W Jarecki, Patrick L Sheets, James O Jackson, Yucheng Xiao, Theodore R CumminsAbstract:Alternative splicing is known to alter pharmacological sensitivities, kinetics, channel distribution under pathological conditions, and developmental regulation of VGSCs. Mutations that alter channel properties in Na(V)1.7 have been genetically implicated in patients with bouts of extreme pain classified as inherited erythromelalgia (IEM) or paroxysmal extreme pain disorder (PEPD). Furthermore, patients with IEM or PEPD report differential age onsets. A recent study reported that alternative splicing of Na(V)1.7 exon 5 affects ramp current properties. Since IEM and PEPD mutations also alter Na(V)1.7 ramp current properties we speculated that alternative splicing might impact the functional consequences of IEM or PEPD mutations. We compared the effects alternative splicing has on the biophysical properties of Na(V)1.7 wild-type, IEM (I136V) and PEPD (I1461T) channels. Our major findings demonstrate that although the 5A splice variant of the IEM channel had no functional impact, the 5A splice variant of the PEPD channel significantly hyperpolarized the activation curve, slowed deactivation and closed-state inactivation, shifted the ramp current activation to more hyperpolarized potentials, and increased ramp current amplitude. We hypothesize a D1/S3-S4 charged residue difference between the 5N (Asn) and the 5A (Asp) variants within the coding region of exon 5 may contribute to shifts in channel activation and deactivation. Taken together, the additive effects observed on ramp currents from exon 5 splicing and the PEPD mutation (I1461T) are likely to impact the disease phenotype and may offer insight into how alternative splicing may affect specific intramolecular interactions critical for voltage-dependent gating.
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impact of nav1 7 PEPD missense mutations that slow the rate of inactivation on sensory neuronal resurgent sodium currents
Biophysical Journal, 2009Co-Authors: Brian W Jarecki, James O Jackson, Andrew D Piekarz, Theodore R CumminsAbstract:Voltage-gated sodium (Nav1.1-9) channels are dynamic transmembrane proteins that, in response to changes in the potential across the lipophilic cell membrane, undergo specific conformational (gating) modifications, between ion-conducting (open) and non-conducting (closed and inactivated) states, to selectively conduct sodium ions through their aqueous pore. Importantly, changes in these voltage-dependent gating properties can impact action potential (AP) characteristics. TTX-sensitive sodium channels in cerebellar neurons can produce resurgent currents (Raman & Bean, 1997), intriguing currents that are re-activated during intermediate repolarizations following strong, but short, depolarizations. We observe resurgent currents in some DRG neurons and found that wild-type Nav1.6 but not wild-type Nav1.7 channels can generate resurgent currents in DRG neurons (Cummins et al., 2005). It has been demonstrated that, in cerebellar neurons from Nav1.6-null mice, slowing inactivation of the remaining Nav current can induce resurgent currents (Grieco & Raman, 2004). Interestingly, single-point missense mutations in the SCN9A gene that encode for Nav1.7, implicated in paroxysmal extreme pain disorder (PEPD), slow the rate of Nav1.7 inactivation (Jarecki et al., 2008). Therefore, we hypothesized that slowing of Nav1.7 by PEPD mutations might induce abnormal resurgent currents, thus altering AP properties. To explore this hypothesis, we transiently transfected adult rat DRG neurons with a TTX-resistant form of human Nav1.7-wild-type or PEPD mutant cDNA and rat Nav1.8-targeted shRNA. Voltage-dependent properties were observed using whole-cell voltage-clamp electrophysiology and AP generation was tested using current-clamp electrophysiology. Recordings were made in the presence and absence of extracellular TTX. These experiments should yield insight into (1) the mechanism of resurgent sodium current generation in DRG neurons, (2) a potential additive effect in channel dysfunction observed in PEPD, and (3) how these mutant channels contribute to alterations in AP characteristics.
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paroxysmal extreme pain disorder mutations within the d3 s4 s5 linker of nav1 7 cause moderate destabilization of fast inactivation
The Journal of Physiology, 2008Co-Authors: Brian W Jarecki, Patrick L Sheets, James O Jackson, Theodore R CumminsAbstract:Single-point missense mutations in the peripheral neuronal voltage-gated sodium channel Nav1.7 are implicated in the painful inherited neuropathy paroxysmal extreme pain disorder (PEPD). The Nav1.7 PEPD mutations are located in regions of the channel suggested to play important roles in fast inactivation. PEPD mutations in the putative inactivation gate have been reported to significantly impair fast inactivation, resulting in pronounced persistent currents. However, PEPD mutations in the S4–S5 linker of domain 3 (D3/S4–S5) had not been characterized and the roles of specific residues in this linker in channel gating are unclear. We functionally characterized two of the D3/S4–S5 PEPD mutations (V1298F and V1299F) and compared their effects on gating to an adjacent non-PEPD mutation (V1300F) and the I1461T PEPD mutation, located in the putative inactivation gate. The primary effect of the V1298F and V1299F mutations is to shift the voltage dependence of fast inactivation by ∼20 mV in the depolarizing direction. We observed a similar effect with the PEPD mutation I1461T. Interestingly, while all three PEPD mutations increased persistent currents, the relative amplitudes (∼6% of peak) were much smaller than previously reported for the I1461T mutation. In contrast, the main effect of the V1300F mutation was a depolarizing shift in the voltage dependence of activation. These data demonstrate that (1) mutations within D3/S4–S5 affect inactivation of Nav1.7 in a residue-specific manner and (2) disruption of the fast-inactivated state by PEPD mutations can be more moderate than previously indicated, which has important implications for the pathophysiology of PEPD.
Yuesheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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abstract 552 PEPD is an essential regulator of p53 tumor suppressor
Cancer Research, 2018Co-Authors: Lu Yang, Arup Bhattacharya, Yuesheng ZhangAbstract:Peptidase D (PEPD), also known as prolidase among other names, is an enzyme that hydrolyzes dipeptides with proline or hydroxyproline at the carboxy terminus and is believed to be important for collagen metabolism, as proline and hydroxyproline are very abundant in collagen. Interestingly, we recently found that eliminating cellular PEPD causes cell death and tumor regression due to p53 activation. Here, we show that PEPD binds to and suppresses over half of nuclear and cytoplasmic p53 under normal conditions, independent of its enzymatic activity. PEPD binds to the proline-rich domain in p53, which inhibits phosphorylation of nuclear p53 and MDM2-mediated mitochondrial translocation of nuclear and cytoplasmic p53. Indeed, PEPD competes with MDM2 for p53 binding. However, the PEPD-p53 complex is critical for p53 response to stress, as stress signals doxorubicin (DOX) and hydrogen peroxide each must free p53 from PEPD in order to achieve robust p53 activation, which is mediated by reactive oxygen species. Thus, PEPD stores p53 for stress response, but this also renders cells dependent on PEPD for survival as it suppresses p53. Our results reveal a major p53 regulatory mechanism and a critical physiological function of PEPD. The p53-PEPD system likely operates in most if not all cells, since both p53 and PEPD are expressed ubiquitously. Disrupting PEPD suppression of p53 may be an important therapeutic strategy in cancer, as our data show that PEPD knockdown by RNA interference in tumors in mice causes p53 activation in the tumor tissues and tumor regression. Our study also reveals a previously unrecognized anticancer mechanism of DOX. We show that the key step in DOX-induced p53 activation is the disruption of p53 association with PEPD via reactive oxygen species. This finding also raises the intriguing question of whether other stress-inducing anticancer agents also disrupt the PEPD-p53 complex for p53 activation and suggests that antioxidants may inhibit the anticancer activity of DOX and other agents by inhibiting p53 separation from PEPD. This work is supported by NCI grants and Roswell Park Alliance Foundation Grants. Citation Format: Lu Yang, Yun Li, Arup Bhattacharya, Yuesheng Zhang. PEPD is an essential regulator of p53 tumor suppressor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 552.
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PEPD is a pivotal regulator of p53 tumor suppressor
Nature Communications, 2017Co-Authors: Lu Yang, Arup Bhattacharya, Yuesheng ZhangAbstract:p53 tumor suppressor responds to various cellular stresses and regulates cell fate. Here, we show that peptidase D (PEPD) binds and suppresses over half of nuclear and cytoplasmic p53 under normal conditions, independent of its enzymatic activity. Eliminating PEPD causes cell death and tumor regression due to p53 activation. PEPD binds to the proline-rich domain in p53, which inhibits phosphorylation of nuclear p53 and MDM2-mediated mitochondrial translocation of nuclear and cytoplasmic p53. However, the PEPD-p53 complex is critical for p53 response to stress, as stress signals doxorubicin and H2O2 each must free p53 from PEPD in order to achieve robust p53 activation, which is mediated by reactive oxygen species. Thus, PEPD stores p53 for the stress response, but this also renders cells dependent on PEPD for survival, as it suppresses p53. This finding provides further understanding of p53 regulation and may have significant implications for the treatment of cancer and other diseases.
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abstract p6 07 04 targeting erbb2 with human PEPD
Cancer Research, 2015Co-Authors: Lu Yang, Arup Bhattacharya, Yuesheng ZhangAbstract:ErbB2, also known as Her2 or Neu, belongs to the ErbB family of plasma membrane-bound receptor tyrosine kinases, which also include ErbB1, ErbB3 and ErbB4. ErbB2 is best known for its involvement in human breast cancer. ErbB2 gene amplification occurs in ∼20% of breast cancer, and ErbB2 amplification or overexpression is a strong predictor of poor disease prognosis. ErbB2-targeted therapies, particularly humanized monoclonal antibody trastuzumab (Ttzm) in combination with chemotherapy, have shown considerable clinical efficacy. However, primary and secondary resistance remains a clinical challenge, and Ttzm, produced in mammalian cells, is very expensive. We have found that human prolidase, also known as peptidase D (PEPD) among several other names, binds to ErbB2 with high affinity (Kd = ∼7 nM) and binds as a homodimer (493 amino acids per subunit) to subdomain 3 in the extracellular domain of ErbB2. Each monomer of PEPD binds to one copy of ErbB2. However, PEPD is a weak ErbB1 binder (Kd = ∼5 μM) and does not bind to ErbB3 or ErbB4. PEPD is the first-ever natural ligand of ErbB2, and unlike the other ligands of ErbB receptors, it is devoid of an EGF motif. PEPD has been long known to hydrolyze dipeptides with proline or hydroxylproline at the carboxy terminus, but the dipeptidase activity of PEPD is not involved in ErbB2/ErbB1 modulation. In cells overexpressing ErbB2, where both activated dimers and inactive monomers of ErbB2 exist, as ErbB2 overexpression causes spontaneous dimerization, auto-tyrosine phosphorylation and recruitment and activation of downstream signals, PEPD rapidly binds to ErbB2 homodimers ( ∼30 min), but this binding causes ErbB2 dimerization, ErbB2 phosphorylation and downstream signaling. PEPD binding to ErbB2 subsequently causes pronounced ErbB2 depletion, resulting from its internalization and degradation. PEPD also strongly inhibits the DNA synthesis, anchorage-independent growth and invasion of cells that overexpress ErbB2, but has no effect on cells without overexpression of ErbB2. In fact, cells become sensitized to inhibition by PEPD upon achieving stable ErbB2 overexpression. Thus, the overall impact of PEPD on ErbB2 is inhibitory, and PEPD targets cells addicted to ErbB2. In ErbB2-overexpressing cells, at equimolar concentrations, PEPD was more effective than Ttzm in driving ErbB2 depletion, but is weaker than Ttzm in stimulating ErbB2 phosphorylation. In mouse tumor models, PEPD administered by intraperitoneal injection (Monday, Wednesday, Friday) at 0.2-2 mg/kg body weight strongly inhibited the growth of ErbB2-overexpressing tumors, but had no impact on tumors without ErbB2 overexpression, and the PEPD-treated mice showed no adverse effects. Given that the findings described above were made using human PEPD generated in bacteria, there is a distinct possibility that recombinant human PEPD may be a low cost alternative to Ttzm. Further investigation of the antitumor activity of PEPD and its modulation of ErbB2 signaling is warranted. Citation Format: Lu Yang, Yun Li, Arup Bhattacharya, Yuesheng Zhang. Targeting ErbB2 with human PEPD [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-07-04.
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Inhibition of ERBB2-overexpressing Tumors by Recombinant Human Prolidase and Its Enzymatically Inactive Mutant
Elsevier, 2015Co-Authors: Lu Yang, Arup Bhattacharya, Yuesheng ZhangAbstract:ERBB2 is an oncogenic receptor tyrosine kinase overexpressed in a subset of human breast cancer and other cancers. We recently found that human prolidase (PEPD), a dipeptidase, is a high affinity ERBB2 ligand and cross-links two ERBB2 monomers. Here, we show that recombinant human PEPD (rhPEPD) strongly inhibits ERBB2-overexpressing tumors in mice, whereas it does not impact tumors without ERBB2 overexpression. rhPEPD causes ERBB2 depletion, disrupts oncogenic signaling orchestrated by ERBB2 homodimers and heterodimers, and induces apoptosis. The impact of enzymatically-inactive mutant rhPEPDG278D on ERBB2 is indistinguishable from that of rhPEPD, but rhPEPDG278D is superior to rhPEPD for tumor inhibition. The enzymatic function of rhPEPD stimulates HIF-1α and other pro-survival factors in tumors, which likely attenuates its antitumor activity. rhPEPDG278D is also attractive in that it may not interfere with the physiologic function of endogenous PEPD in normal cells. Collectively, we have identified a human protein as an inhibitory ERBB2 ligand that inhibits ERBB2-overexpressing tumors in vivo. Several anti-ERBB2 agents are on the market but are hampered by drug resistance and high drug cost. rhPEPDG278D may synergize with these agents and may also be highly cost-effective, since it targets ERBB2 with a different mechanism and can be produced in bacteria
Chienhsiun Chen - One of the best experts on this subject based on the ideXlab platform.
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meta analysis of genome wide association studies identifies eight new loci for type 2 diabetes in east asians
Nature Genetics, 2012Co-Authors: Chienhsiun Chen, Cheng Hu, Jirong Long, Fumihiko Takeuchi, Ying Wu, Min Jin Go, Toshimasa Yamauchi, Yicheng Chang, Soo Heon KwakAbstract:We conducted a three-stage genetic study to identify susceptibility loci for type 2 diabetes (T2D) in east Asian populations. We followed our stage 1 meta-analysis of eight T2D genome-wide association studies (6,952 cases with T2D and 11,865 controls) with a stage 2 in silico replication analysis (5,843 cases and 4,574 controls) and a stage 3 de novo replication analysis (12,284 cases and 13,172 controls). The combined analysis identified eight new T2D loci reaching genome-wide significance, which mapped in or near GLIS3, PEPD, FITM2-R3HDML-HNF4A, KCNK16, MAEA, GCC1-PAX4, PSMD6 and ZFAND3. GLIS3, which is involved in pancreatic beta cell development and insulin gene expression, is known for its association with fasting glucose levels. The evidence of an association with T2D for PEPD and HNF4A has been shown in previous studies. KCNK16 may regulate glucose-dependent insulin secretion in the pancreas. These findings, derived from an east Asian population, provide new perspectives on the etiology of T2D.
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meta analysis of genome wide association studies identifies eight new loci for type 2 diabetes in east asians
Nature Genetics, 2012Co-Authors: Yoon Shin Cho, Chienhsiun Chen, Jirong Long, Fumihiko Takeuchi, Toshimasa Yamauchi, Yicheng Chang, Rick Tweehee Ong, Xueling Sim, Soo Heon KwakAbstract:We conducted a three-stage genetic study to identify susceptibility loci for type 2 diabetes (T2D) in east Asian populations. We followed our stage 1 meta-analysis of eight T2D genome-wide association studies (6,952 cases with T2D and 11,865 controls) with a stage 2 in silico replication analysis (5,843 cases and 4,574 controls) and a stage 3 de novo replication analysis (12,284 cases and 13,172 controls). The combined analysis identified eight new T2D loci reaching genome-wide significance, which mapped in or near GLIS3, PEPD, FITM2-R3HDML-HNF4A, KCNK16, MAEA, GCC1-PAX4, PSMD6 and ZFAND3. GLIS3, which is involved in pancreatic beta cell development and insulin gene expression, is known for its association with fasting glucose levels. The evidence of an association with T2D for PEPD and HNF4A has been shown in previous studies. KCNK16 may regulate glucose-dependent insulin secretion in the pancreas. These findings, derived from an east Asian population, provide new perspectives on the etiology of T2D.
Chunjung Chen - One of the best experts on this subject based on the ideXlab platform.
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identification and analysis of a novel mutation in PEPD gene in two kashmiri siblings with prolidase enzyme deficiency
Gene, 2013Co-Authors: Riyaz Ahmad Pandit, Chunjung Chen, Tariq Ahmad Butt, Naquibul IslamAbstract:Abstract Prolidase deficiency (PD) is a rare inborn disorder of collagen metabolism characterized by chronic recurrent cutaneous ulceration. We report a novel 3 bp insertion in the 12th exon of the PEPD gene in two Kashmiri siblings with prolidase deficiency phenotype. This mutation results in addition of an extra alanine residue at the amino-acid position number 304 of prolidase peptide. The structural analysis showed that this Ala insertion is located at the helix (a.a. 300–320), which contains several important hydrogen bonds between residues essential for structural folding for the enzyme activity. In silico analysis suggests that this insertion mutation might distort or bend the helical feature to affect the hydrogen-bond network between residues of neighboring secondary structures and deform the metal-binding geometry of the enzyme. Although approximately 70 PEPD gene mutations and polymorphisms have been reported in various ethnic groups, we however report, for the first time, the identification of insertion mutation in human the PEPD gene.
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crystal structure and mutational analysis of aminoacylhistidine dipeptidase from vibrio alginolyticus reveal a new architecture of m20 metallopeptidases
Journal of Biological Chemistry, 2010Co-Authors: Chinyuan Chang, Yin Cheng Hsieh, Tingyi Wang, Yichin Chen, Yu Kuo Wang, Ting Wei Chiang, Yi Ju Chen, Chenghsiang Chang, Chunjung ChenAbstract:Aminoacylhistidine dipeptidases (PEPD, EC 3.4.13.3) belong to the family of M20 metallopeptidases from the metallopeptidase H clan that catalyze a broad range of dipeptide and tripeptide substrates, including L-carnosine and L-homocarnosine. Homocarnosine has been suggested as a precursor for the neurotransmitter γ-aminobutyric acid (GABA) and may mediate the antiseizure effects of GABAergic therapies. Here, we report the crystal structure of PEPD from Vibrio alginolyticus and the results of mutational analysis of substrate-binding residues in the C-terminal as well as substrate specificity of the PEPD catalytic domain-alone truncated protein PEPD(CAT). The structure of PEPD was found to exist as a homodimer, in which each monomer comprises a catalytic domain containing two zinc ions at the active site center for its hydrolytic function and a lid domain utilizing hydrogen bonds between helices to form the dimer interface. Although the PEPD is structurally similar to PepV, which exists as a monomer, putative substrate-binding residues reside in different topological regions of the polypeptide chain. In addition, the lid domain of the PEPD contains an "extra" domain not observed in related M20 family metallopeptidases with a dimeric structure. Mutational assays confirmed both the putative di-zinc allocations and the architecture of substrate recognition. In addition, the catalytic domain-alone truncated PEPD(CAT) exhibited substrate specificity to l-homocarnosine compared with that of the wild-type PEPD, indicating a potential value in applications of PEPD(CAT) for GABAergic therapies or neuroprotection.
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purification crystallization and preliminary x ray analysis of an aminoacylhistidine dipeptidase PEPD from vibrio alginolyticus
Acta Crystallographica Section F-structural Biology and Crystallization Communications, 2009Co-Authors: Chinyuan Chang, Yin Cheng Hsieh, Tingyi Wang, Chunjung ChenAbstract:The aminoacylhistidine dipeptidase (PEPD) protein encoded by Vibrio alginolyticus PEPD was successfully overexpressed and characterized and the putative active-site residues responsible for metal binding and catalysis were identified. The purified enzyme contained two zinc ions per monomer. The recombinant dipeptidase enzyme, which was identified as a homodimer in solution, exhibited broad substrate specificity for Xaa-His dipeptides, with highest activity towards the His-His dipeptide. The purified protein was crystallized using the hanging-drop vapour-diffusion method. Preliminary crystallographic analysis showed that the crystal belonged to space group P61 or P65, with unit-cell parameters a = b = 80.42, c = 303.11 A. The crystal contained two molecules per asymmetric unit and the predicted solvent content was 53.4%.