The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Hongyang Wang - One of the best experts on this subject based on the ideXlab platform.
-
Involvement of β3A Subunit of Adaptor Protein‐3 in Intracellular Trafficking of Receptor‐like Protein Tyrosine Phosphatase PCP‐2
Acta biochimica et biophysica Sinica, 2007Co-Authors: Hui Dong, Hong Yuan, Weirong Jin, Yan Shen, Hongyang WangAbstract:PCP-2 is a human receptor-like protein tyrosine phosphatase and a member of the MAM Domain family cloned in human pancreatic adenocarcinoma cells. Previous studies showed that PCP-2 directly interacted with beta-catenin through the juxtamembrane Domain, dephosphorylated beta-catenin and played an important role in the regulation of cell adhesion. Recent study showed that PCP-2 was also involved in the repression of beta-catenin-induced transcriptional activity. Here we describe the interactions of PCP-2 with the beta3A subunit of adaptor protein (AP)-3 and sorting nexin (SNX) 3. These protein complexes were detected using the yeast two-hybrid assay with the juxtamembrane and membrane-proximal catalytic Domain of PCP-2 as "bait" Both AP-3 and SNX3 are molecules involved in intracellular trafficking of membrane receptors. The association between the beta3A subunit of AP-3 and PCP-2 was further confirmed in MAMmalian cells. Our results suggested a possible mechanism of intracellular trafficking of PCP-2 mediated by AP-3 and SNX3 which might participate in the regulation of PCP-2 functions.
-
Structural basis of interaction between protein tyrosine phosphatase PCP-2 and β-catenin
Science in China. Series C Life sciences, 2005Co-Authors: He-xin Yan, Peng Zhang, Hui Dong, Liang Tang, Xiu-hua Qiu, Hongyang WangAbstract:PCP-2 is a member of receptor-like protein tyrosine phosphatase of the MAM Domain family. To investigate which part of PCP-2 was involved in its interaction with β-catenin, we constructed various deletion mutants of PCP-2. These PCP-2 mutants and wild-type PCP-2 were co-transfected into BHK-21 cells with β-catenin individually. Anin vivo binding assay revealed that the expression of wild-type PCP-2, PCP-2 ΔC1C2 (deleted PCP-2 without both PTP Domains) and PCP-2 ΔC2 (deleted PCP-2 without the second PTP Domain) could be immunoprecipitated by anti-catenin antibody in every co-transfection, but PCP-2 EXT (deleted PCP-2 without the juxtamembrane region and both PTP Domains) was missing, which implied that PCP-2 and β-catenin could associate directly and the juxtamembrane region in PCP-2 was sufficient for the process.
-
Physical and functional interaction between receptor-like protein tyrosine phosphatase PCP-2 and beta-catenin.
Biochemistry, 2002Co-Authors: He-xin Yan, Peng Zhang, Hui Dong, Jin-zhang Zeng, Hui-fang Cao, Hongyang WangAbstract:We have previously identified a human receptor protein tyrosine phosphatase of the MAM Domain family, termed PCP-2, in human pancreatic adenocarcinoma cells and found that this protein was colocalized with β-catenin and E-cadherin at cell junctions [Wang, H.-Y., et al. (1996) Oncogene 12, 2555−2562]. Its intracellular part consists of two tandem phosphatase Domains and a relatively large juxtamembrane region that is homologous to the conserved intracellular Domain of cadherins, suggesting a role in the regulation of cell adhesion. This study reports that PCP-2 was endogenously expressed at the cell surface and upregulated with increased cell density. An in vivo binding assay revealed that PCP-2 could directly interact with β-catenin through a region in the juxtamembrane Domain. Tyrosine phosphorylation of β-catenin by EGF or active SrcY527F did not disrupt the formation of the PCP-2−β-catenin complex, while PCP-2 in this complex could cause a significant reduction in the phosphorylation level in β-catenin...
-
Characterization of PCP-2, a novel receptor protein tyrosine phosphatase of the MAM Domain family.
Oncogene, 1996Co-Authors: Hongyang Wang, Lian Z, Markus M. Lerch, Chen Z, Xie W, Axel UllrichAbstract:DNA sequences encoding a novel member of the receptor protein tyrosine phosphatase (R-PTP) family, termed PCP-2, were identified in a human pancreatic adenocarcinoma cDNA library. Human PCP-2 cDNA predicts a protein of 1430 amino acids with a calculated Mr of 160 kDa. The predicted PCP-2 enzyme consists of a 740 amino acid extracellular region, a single transmembrane Domain, and a 666 amino acid intracellular portion. The extracellular sequence contains a MAM (meprin/A5/PTPmu) Domain, an immunoglobulin-like Domain and four fibronectin type III-like repeats, suggesting that it is a member of the PTPkappa and PTPmu subfamily. The intracellular region contains two tandemly-repeated protein tyrosine phosphatase Domains. Northern blot analyses revealed a single transcript of 5.5 kilobases, which is expressed at different levels in many human tissues except spleen and placenta. Upon transfection of PCP-2 cDNA into human embryonic kidney fibroblast 293 cells, a protein with an apparent Mr of 180 000 was detected by immunoblot analysis. This size was reduced to the predicted Mr upon treatment with endoglycosidase F, indicating that PCP-2 is glycosylated and, hence, expressed at the cell surface. A potential role of PCP-2 in cell-cell recognition and adhesion is supported by its co-localization with cell adhesion molecules, such as catenin and E-cadherin, at sites of cell-cell contact.
Susann M. Brady-kalnay - One of the best experts on this subject based on the ideXlab platform.
-
Cancer-derived mutations in the fibronectin III repeats of PTPRT/PTPρ inhibit cell-cell aggregation
Cell communication & adhesion, 2010Co-Authors: Peng Zhang, Susann M. Brady-kalnay, Scott Becka, Sonya E.l. Craig, David T. Lodowski, Zhenghe WangAbstract:AbstractThe receptor protein tyrosine phosphatase T PTPρ is the most frequently mutated tyrosine phosphatase in human cancer. PTPρ mediates homophilic cell-cell aggregation. In its extracellular region, PTPρ has cell adhesion molecule–like motifs, including a MAM Domain, an immunoglobulin Domain, and four fibronectin type III (FNIII) repeats. Tumor-derived mutations have been identified in all of these extracellular Domains. Previously, the authors determined that tumor-derived mutations in the MAM and immunoglobulin Domains of PTPρ reduce homophilic cell-cell aggregation. In this paper, the authors describe experiments in which the contribution of the FNIII repeats to PTPρ-mediated cell-cell adhesion was evaluated. The results demonstrate that deletion of the FNIII repeats of PTPρ result in defective cell-cell aggregation. Furthermore, all of the tumor-derived mutations in the FNIII repeats of PTPρ also disrupt cell-cell aggregation. These results further support the hypothesis that mutational inactivati...
-
BCCIP associates with the receptor protein tyrosine phosphatase PTPmu.
Journal of cellular biochemistry, 2008Co-Authors: Polly J. Phillips-mason, Tracy Mourton, Denice L. Major, Susann M. Brady-kalnayAbstract:Protein tyrosine phosphorylation is recognized as an important mode of regulation for many cellular functions. The tyrosine phosphorylation state of cellular proteins is determined by the coordinated activity of protein tyrosine kinases (PTKs) [Machida et al., 2003; Pawson, 2002] and protein tyrosine phosphatases (PTPs)[Tonks, 2006]. PTPs are a diverse group of enyzmes that exist as either soluble cytoplasmic forms or as transmembrane, receptor-like proteins [Tonks, 2006]. In this manuscript, we focus on the receptor protein tyrosine phosphatase (RPTP) PTPμ. The extracellular segment of PTPμ contains sequences found in several cell adhesion molecules including a MAM Domain, an Ig Domain and four FNIII repeats. As suggested by the presence of these Domains, PTPμ mediates cell-cell adhesion via homophilic binding [Brady-Kalnay et al., 1993; Gebbink et al., 1993b] meaning the “ligand” for PTPμ is an identical PTPμ molecule on an adjacent cell. The juxtamembrane Domain of PTPμ contains a region homologous to the conserved intracellular Domain of the cadherins. Cadherins are calcium-dependent cell-cell adhesion molecules that associate with the actin cytoskeleton via catenins [Gumbiner, 2005; Lilien, 2005]. Members of the catenin family bind the intracellular Domain of cadherins and include α-catenin, β-catenin, plakoglobin and p120. PTPμ associates with cadherin-catenin complexes [Brady-Kalnay et al., 1998; Brady-Kalnay et al., 1995; Hiscox and Jiang, 1998; Sui et al., 2005]. Specifically, PTPμ interacts with classical cadherins such as N-cadherin, E-cadherin and R-cadherin [Brady-Kalnay et al., 1998] and VE-cadherin [Sui et al., 2005]. PTPμ has been shown also to interact with p120 catenin [Zondag et al., 2000]. The intracellular Domain of PTPμ contains two conserved catalytic Domains. Of these two phosphatase Domains, only the membrane proximal Domain possesses catalytic activity [Gebbink et al., 1993a]. PTPμ has been implicated previously in the regulation of E-cadherin-mediated cell-cell adhesion [Hellberg et al., 2002] and both N-cadherin and E-cadherin-mediated neurite outgrowth [Burden-Gulley and Brady-Kalnay, 1999; Oblander et al., 2007]. Furthermore, PTPμ has been shown to interact directly with IQGAP1 [Phillips-Mason et al., 2006], a protein involved in the regulation of cadherin-mediated cell-cell adhesion [Kuroda et al., 1998; Li et al., 1999]. In addition to PTPμ’s role in the regulation of cadherin function, PTPμ appears to either directly or indirectly regulate protein kinase C. In support of this, PTPμ was found to interact with the scaffolding protein RACK1 (receptor for activated C-kinase) in a yeast two-hybrid screen [Mourton et al., 2001], and both PTPμ-mediated neurite outgrowth and PTPμ-mediated axon guidance of retinal ganglion cells require PKCδ activity [Ensslen and Brady-Kalnay, 2004; Rosdahl et al., 2002]. In an effort to elucidate PTPμ-mediated signaling events, we set out to identify PTPμ-interacting proteins using a modified yeast two-hybrid screen in which we co-expressed PTPμ with a constitutively active Src tyrosine kinase. The presence of active Src increased the potential to identify proteins that interact in response to tyrosine phosphorylation. In this manuscript, we describe BCCIP as a PTPμ-interacting protein isolated by this modified two-hybrid screen. BCCIP was originally described as TOK-1 (twenty-one and CDK associated protein-1) based on its ability to bind the cyclin-dependent kinase (CDK)- inhibitor, p21Waf1/Cip1 (referred to as p21 hereafter) in a cyclin/CDK2/p21 ternary complex and to enhance the inhibitory activity of p21 on CDK2 [Ono et al., 2000]. Independently, a second group identified BCCIP as a protein that interacts with the internal conserved region of BRCA2, and showed that overexpression of BCCIP inhibits the growth of some tumor cell lines [Liu et al., 2001]. TOK-1 and BCCIP are identical proteins existing as two isoforms in humans, BCCIPα and BCCIPβ [Liu et al., 2001; Ono et al., 2000]. In addition to interacting with p21, BCCIP has been shown recently to regulate p21 expression in a p53-dependent manner [Meng et al., 2004b]. In lower organisms, including rodents, only one BCCIP isoform exists [Lu et al., 2005]. A yeast homolog of BCCIP, Bcp1 has been identified and demonstrated to function in the nuclear export of a protein involved in the regulation of the yeast PI4P 5-kinase, Mss4 [Audhya and Emr, 2003]. In this manuscript, we demonstrate a direct interaction between PTPμ and BCCIP. Furthermore, we show BCCIPα is tyrosine phosphorylated in vitro and a substrate for PTPμ. The best characterized biological function of PTPμ is neurite outgrowth. The catalytic activity of PTPμ is required for it to promote neurite outgrowth of nasal retinal ganglion cells and induce repulsion of temporal retinal ganglion cells [Ensslen-Craig and Brady-Kalnay, 2005]. In this manuscript, we demonstrate that expression of a BCCIP antisense construct blocks both permissive and repulsive activities of PTPμ in neurite outgrowth assays of retinal ganglion cells, suggesting BCCIP and PTPμ are in a common signaling pathway.
-
Receptor protein tyrosine phosphatase PTPmu associates with cadherins and catenins in vivo.
The Journal of cell biology, 1995Co-Authors: Susann M. Brady-kalnay, David L. Rimm, Nicholas K. TonksAbstract:The extracellular segment of the receptor-type type protein tyrosine phosphatase PTPmu, possesses an MAM Domain, an immunoglobulin Domain, and four fibronectin type-III repeats. It binds homophilically, i.e., PTPmu on the surface of one cell binds to PTPmu on an apposing cell, and the binding site lies within the immunoglobulin Domain. The intracellular segment of PTPmu has two PTP Domains and a juxtamembrane segment that is homologous to the conserved intracellular Domain of the cadherins. In cadherins, this segment interacts with proteins termed catenins to mediate association with the actin cytoskeleton. In this article, we demonstrate that PTPmu associates with a complex containing cadherins, alpha- and beta-catenin in mink lung (MvLu) cells, and in rat heart, lung, and brain tissues. Greater than 80% of the cadherin in the cell is cleared from Triton X-100 lysates of MvLu cells after immunoprecipitation with antibodies to PTPmu; however, the complex is dissociated when lysates are prepared in more stringent, SDS-containing RIPA buffer. In vitro binding studies demonstrated that the intracellular segment of PTPmu binds directly to the intracellular Domain of E-cadherin, but not to alpha- or beta-catenin. Consistent with their ability to interact in vivo, PTPmu, cadherins, and catenins all localized to points of cell-cell contact in MvLu cells, as assessed by immunocytochemical staining. After pervanadate treatment of MvLu cells, which inhibits cellular tyrosine phosphatase activity including PTPmu, the cadherins associated with PTPmu are now found in a tyrosine-phosphorylated form, indicating that the cadherins may be an endogenous substrate for PTPmu. These data suggest that PTPmu may be one of the enzymes that regulates the dynamic tyrosine phosphorylation, and thus function, of the cadherin/catenin complex in vivo.
-
Identification of the homophilic binding site of the receptor protein tyrosine phosphatase PTP mu.
The Journal of biological chemistry, 1994Co-Authors: Susann M. Brady-kalnay, Nicholas K. TonksAbstract:Abstract The receptor-type protein tyrosine phosphatase PTP mu comprises an extracellular segment containing a MAM Domain, an immunoglobulin Domain and four fibronectin type III repeats, a transmembrane segment, and two intracellular PTP Domains. We have previously shown that PTP mu binds homophilically, i.e. PTP mu on the surface of one cell binds to PTP mu on an apposing cell, and that the extracellular segment alone is sufficient for homophilic binding. In this study we report that in MvLu cells PTP mu is proteolytically processed into two noncovalently associated fragments, one comprising most of the extracellular segment (approximately 100 kDa) and the other containing predominantly the transmembrane and intracellular portions (approximately 100 kDa). We have also identified the homophilic binding site within the extracellular segment. We have generated, expressed, and purified various fragments of the extracellular segment of PTP mu and have used fluorescent beads (Covaspheres) coated with these fragments in three binding assays: (i) measurement of bead aggregation, (ii) binding of beads to surfaces of dishes coated with purified PTP mu, or (iii) binding to MvLu cells. Only beads coated with recombinant fragments that contained the immunoglobulin Domain underwent aggregation or bound to surfaces displaying PTP mu, suggesting that neither the MAM Domain nor the fibronectin type III repeats bound homophilically in these assays. The fragment containing the Ig Domain alone bound as well as any other Ig Domain-containing fragment, suggesting that the Ig Domain is both necessary and sufficient for homophilic binding under these conditions.
Nicholas K. Tonks - One of the best experts on this subject based on the ideXlab platform.
-
Receptor protein tyrosine phosphatase PTPmu associates with cadherins and catenins in vivo.
The Journal of cell biology, 1995Co-Authors: Susann M. Brady-kalnay, David L. Rimm, Nicholas K. TonksAbstract:The extracellular segment of the receptor-type type protein tyrosine phosphatase PTPmu, possesses an MAM Domain, an immunoglobulin Domain, and four fibronectin type-III repeats. It binds homophilically, i.e., PTPmu on the surface of one cell binds to PTPmu on an apposing cell, and the binding site lies within the immunoglobulin Domain. The intracellular segment of PTPmu has two PTP Domains and a juxtamembrane segment that is homologous to the conserved intracellular Domain of the cadherins. In cadherins, this segment interacts with proteins termed catenins to mediate association with the actin cytoskeleton. In this article, we demonstrate that PTPmu associates with a complex containing cadherins, alpha- and beta-catenin in mink lung (MvLu) cells, and in rat heart, lung, and brain tissues. Greater than 80% of the cadherin in the cell is cleared from Triton X-100 lysates of MvLu cells after immunoprecipitation with antibodies to PTPmu; however, the complex is dissociated when lysates are prepared in more stringent, SDS-containing RIPA buffer. In vitro binding studies demonstrated that the intracellular segment of PTPmu binds directly to the intracellular Domain of E-cadherin, but not to alpha- or beta-catenin. Consistent with their ability to interact in vivo, PTPmu, cadherins, and catenins all localized to points of cell-cell contact in MvLu cells, as assessed by immunocytochemical staining. After pervanadate treatment of MvLu cells, which inhibits cellular tyrosine phosphatase activity including PTPmu, the cadherins associated with PTPmu are now found in a tyrosine-phosphorylated form, indicating that the cadherins may be an endogenous substrate for PTPmu. These data suggest that PTPmu may be one of the enzymes that regulates the dynamic tyrosine phosphorylation, and thus function, of the cadherin/catenin complex in vivo.
-
Identification of the homophilic binding site of the receptor protein tyrosine phosphatase PTP mu.
The Journal of biological chemistry, 1994Co-Authors: Susann M. Brady-kalnay, Nicholas K. TonksAbstract:Abstract The receptor-type protein tyrosine phosphatase PTP mu comprises an extracellular segment containing a MAM Domain, an immunoglobulin Domain and four fibronectin type III repeats, a transmembrane segment, and two intracellular PTP Domains. We have previously shown that PTP mu binds homophilically, i.e. PTP mu on the surface of one cell binds to PTP mu on an apposing cell, and that the extracellular segment alone is sufficient for homophilic binding. In this study we report that in MvLu cells PTP mu is proteolytically processed into two noncovalently associated fragments, one comprising most of the extracellular segment (approximately 100 kDa) and the other containing predominantly the transmembrane and intracellular portions (approximately 100 kDa). We have also identified the homophilic binding site within the extracellular segment. We have generated, expressed, and purified various fragments of the extracellular segment of PTP mu and have used fluorescent beads (Covaspheres) coated with these fragments in three binding assays: (i) measurement of bead aggregation, (ii) binding of beads to surfaces of dishes coated with purified PTP mu, or (iii) binding to MvLu cells. Only beads coated with recombinant fragments that contained the immunoglobulin Domain underwent aggregation or bound to surfaces displaying PTP mu, suggesting that neither the MAM Domain nor the fibronectin type III repeats bound homophilically in these assays. The fragment containing the Ig Domain alone bound as well as any other Ig Domain-containing fragment, suggesting that the Ig Domain is both necessary and sufficient for homophilic binding under these conditions.
Axel Ullrich - One of the best experts on this subject based on the ideXlab platform.
-
furin adam 10 and gamma secretase mediated cleavage of a receptor tyrosine phosphatase and regulation of beta catenin s transcriptional activity
Molecular and Cellular Biology, 2006Co-Authors: Lars Anders, Philipp Mertins, Sven Lammich, Marta Murgia, Dieter Hartmann, Paul Saftig, Christian Haass, Axel UllrichAbstract:Several receptor protein tyrosine phosphatases (RPTPs) are cell adhesion molecules involved in homophilic interactions, suggesting that RPTP outside-in signaling is coupled to cell contact formation. However, little is known about the mechanisms by which cell density regulates RPTP function. We show that the MAM family prototype RPTP is cleaved by three proteases: furin, ADAM 10, and -secretase. Cell density promotes ADAM 10-mediated cleavage and shedding of RPTP. This is followed by -secretase-dependent intramembrane proteolysis of the remaining transmembrane part to release the phosphatase intracellular portion (PIC) from the membrane, thereby allowing its translocation to the nucleus. When cells were treated with leptomycin B, a nuclear export inhibitor, PIC accumulated in nuclear bodies. PIC is an active protein tyrosine phosphatase that binds to and dephosphorylates -catenin, an RPTP substrate. The expression of RPTP suppresses -catenin’s transcriptional activity, whereas the expression of PIC increases it. Notably, this increase required the phosphatase activity of PIC. Thus, both isoforms have acquired opposing roles in the regulation of -catenin signaling. We also found that RPTP, another MAM family member, undergoes -secretasedependent processing. Our results identify intramembrane proteolysis as a regulatory switch in RPTP signaling and implicate PIC in the activation of -catenin-mediated transcription. The phosphorylation of cellular proteins on tyrosine residues is reversible and regulated by the coordinated and competing actions of two enzyme families: protein tyrosine kinases and protein tyrosine phosphatases (PTPs). The PTP family is structurally diverse and includes both receptor-like and cytoplasmic enzymes. The majority of the receptor PTPs (RPTPs) contain two catalytic Domains: a membrane-proximal Domain (D1), which is responsible for mainly catalysis, and a membrane-distal Domain (D2), which contains little or no phosphatase activity (45). The extracellular (E) portion exhibits broad structural variation. The MAM (meprin/A5 glycoprotein/PTPmu) family of RPTPs, including RPTP ,- ,- ,- , and PCP-2, are characterized by the presence of the MAM Domain at their N termini (3, 6, 18, 29, 46). Additional structural features of the extracellular portions involve one immu
-
Characterization of PCP-2, a novel receptor protein tyrosine phosphatase of the MAM Domain family.
Oncogene, 1996Co-Authors: Hongyang Wang, Lian Z, Markus M. Lerch, Chen Z, Xie W, Axel UllrichAbstract:DNA sequences encoding a novel member of the receptor protein tyrosine phosphatase (R-PTP) family, termed PCP-2, were identified in a human pancreatic adenocarcinoma cDNA library. Human PCP-2 cDNA predicts a protein of 1430 amino acids with a calculated Mr of 160 kDa. The predicted PCP-2 enzyme consists of a 740 amino acid extracellular region, a single transmembrane Domain, and a 666 amino acid intracellular portion. The extracellular sequence contains a MAM (meprin/A5/PTPmu) Domain, an immunoglobulin-like Domain and four fibronectin type III-like repeats, suggesting that it is a member of the PTPkappa and PTPmu subfamily. The intracellular region contains two tandemly-repeated protein tyrosine phosphatase Domains. Northern blot analyses revealed a single transcript of 5.5 kilobases, which is expressed at different levels in many human tissues except spleen and placenta. Upon transfection of PCP-2 cDNA into human embryonic kidney fibroblast 293 cells, a protein with an apparent Mr of 180 000 was detected by immunoblot analysis. This size was reduced to the predicted Mr upon treatment with endoglycosidase F, indicating that PCP-2 is glycosylated and, hence, expressed at the cell surface. A potential role of PCP-2 in cell-cell recognition and adhesion is supported by its co-localization with cell adhesion molecules, such as catenin and E-cadherin, at sites of cell-cell contact.
A Rotter - One of the best experts on this subject based on the ideXlab platform.
-
Genomic structure and alternative splicing of murine R2B receptor protein tyrosine phosphatases (PTPκ, μ, ρ and PCP-2)
BMC Genomics, 2004Co-Authors: Julie Besco, A Frostholm, Magdalena C Popesco, Ramana V Davuluri, A RotterAbstract:Background Four genes designated as PTPRK (PTPκ), PTPRL/U (PCP-2), PTPRM (PTPμ) and PTPRT (PTPρ) code for a subfamily (type R2B) of receptor protein tyrosine phosphatases (RPTPs) uniquely characterized by the presence of an N-terminal MAM Domain. These transmembrane molecules have been implicated in homophilic cell adhesion. In the human, the PTPRK gene is located on chromosome 6, PTPRL/U on 1, PTPRM on 18 and PTPRT on 20. In the mouse, the four genes ptprk, ptprl, ptprm and ptprt are located in syntenic regions of chromosomes 10, 4, 17 and 2, respectively. Results The genomic organization of murine R2B RPTP genes is described. The four genes varied greatly in size ranging from ~64 kb to ~1 Mb, primarily due to proportional differences in intron lengths. Although there were also minor variations in exon length, the number of exons and the phases of exon/intron junctions were highly conserved. In situ hybridization with digoxigenin-labeled cRNA probes was used to localize each of the four R2B transcripts to specific cell types within the murine central nervous system. Phylogenetic analysis of complete sequences indicated that PTPρ and PTPμ were most closely related, followed by PTPκ. The most distant family member was PCP-2. Alignment of RPTP polypeptide sequences predicted putative alternatively spliced exons. PCR experiments revealed that five of these exons were alternatively spliced, and that each of the four phosphatases incorporated them differently. The greatest variability in genomic organization and the majority of alternatively spliced exons were observed in the juxtamembrane Domain, a region critical for the regulation of signal transduction. Conclusions Comparison of the four R2B RPTP genes revealed virtually identical principles of genomic organization, despite great disparities in gene size due to variations in intron length. Although subtle differences in exon length were also observed, it is likely that functional differences among these genes arise from the specific combinations of exons generated by alternative splicing.
-
Genomic structure and alternative splicing of murine R2B receptor protein tyrosine phosphatases (PTPκ, μ, ρ and PCP-2)
BMC genomics, 2004Co-Authors: Julie Besco, A Frostholm, Magdalena C Popesco, Ramana V Davuluri, A RotterAbstract:Four genes designated as PTPRK (PTPκ), PTPRL/U (PCP-2), PTPRM (PTPμ) and PTPRT (PTPρ) code for a subfamily (type R2B) of receptor protein tyrosine phosphatases (RPTPs) uniquely characterized by the presence of an N-terminal MAM Domain. These transmembrane molecules have been implicated in homophilic cell adhesion. In the human, the PTPRK gene is located on chromosome 6, PTPRL/U on 1, PTPRM on 18 and PTPRT on 20. In the mouse, the four genes ptprk, ptprl, ptprm and ptprt are located in syntenic regions of chromosomes 10, 4, 17 and 2, respectively. The genomic organization of murine R2B RPTP genes is described. The four genes varied greatly in size ranging from ~64 kb to ~1 Mb, primarily due to proportional differences in intron lengths. Although there were also minor variations in exon length, the number of exons and the phases of exon/intron junctions were highly conserved. In situ hybridization with digoxigenin-labeled cRNA probes was used to localize each of the four R2B transcripts to specific cell types within the murine central nervous system. Phylogenetic analysis of complete sequences indicated that PTPρ and PTPμ were most closely related, followed by PTPκ. The most distant family member was PCP-2. Alignment of RPTP polypeptide sequences predicted putative alternatively spliced exons. PCR experiments revealed that five of these exons were alternatively spliced, and that each of the four phosphatases incorporated them differently. The greatest variability in genomic organization and the majority of alternatively spliced exons were observed in the juxtamembrane Domain, a region critical for the regulation of signal transduction. Comparison of the four R2B RPTP genes revealed virtually identical principles of genomic organization, despite great disparities in gene size due to variations in intron length. Although subtle differences in exon length were also observed, it is likely that functional differences among these genes arise from the specific combinations of exons generated by alternative splicing.
-
Identification and characterization of RPTPρ, a novel RPTPμ/κ-like receptor protein tyrosine phosphatase whose expression is restricted to the central nervous system
Molecular Brain Research, 1998Co-Authors: P E Mcandrew, A Frostholm, R A White, A Rotter, A H BurghesAbstract:We describe the cloning, chromosomal localization and characterization of RPTPρ, a new member of the RPTPμ/κ phosphatase subfamily. Receptor tyrosine phosphatases in this subfamily are comprised of a MAM Domain near the N-terminal, an immunoglobulin-like Domain, four fibronectin type III repeats, a single transmembrane Domain, and a large juxtamembrane segment followed by two intracellular phosphatase Domains. An alternatively spliced mini-exon was identified in the extracellular segment of RPTPρ, between the fourth fibronectin type III repeat and the transmembrane Domain. The RPTRρ gene was mapped to human chromosome 20 and mouse chromosome 2. Northern blot analysis demonstrated that RPTPρ expression was restricted to the central nervous system, and in situ hybridization studies showed that the RPTPρ transcript was distributed throughout the murine brain and spinal cord. Exceptionally high levels of the transcript were present in the cortex and olfactory bulbs during perinatal development, but were down-regulated during postnatal week two. The motifs found in the extracellular segment of type II receptor protein tyrosine phosphatases are commonly found in neural cell adhesion molecules, suggesting that RPTPρ may be involved in both signal transduction and cellular adhesion in the central nervous system.
-
Identification and characterization of RPTP rho, a novel RPTP mu/kappa-like receptor protein tyrosine phosphatase whose expression is restricted to the central nervous system.
Brain research. Molecular brain research, 1998Co-Authors: P E Mcandrew, A Frostholm, R A White, A Rotter, A H BurghesAbstract:We describe the cloning, chromosomal localization and characterization of RPTPrho, a new member of the RPTPmu/kappa phosphatase subfamily. Receptor tyrosine phosphatases in this subfamily are comprised of a MAM Domain near the N-terminal, an immunoglobulin-like Domain, four fibronectin type III repeats, a single transmembrane Domain, and a large juxtamembrane segment followed by two intracellular phosphatase Domains. An alternatively spliced mini-exon was identified in the extracellular segment of RPTPrho, between the fourth fibronectin type III repeat and the transmembrane Domain. The RPTPrho gene was mapped to human chromosome 20 and mouse chromosome 2. Northern blot analysis demonstrated that RPTPrho expression was restricted to the central nervous system, and in situ hybridization studies showed that the RPTPrho transcript was distributed throughout the murine brain and spinal cord. Exceptionally high levels of the transcript were present in the cortex and olfactory bulbs during perinatal development, but were down-regulated during postnatal week two. The motifs found in the extracellular segment of type II receptor protein tyrosine phosphatases are commonly found in neural cell adhesion molecules, suggesting that RPTPrho may be involved in both signal transduction and cellular adhesion in the central nervous system.
