The Experts below are selected from a list of 957 Experts worldwide ranked by ideXlab platform
Boris E Shmukler - One of the best experts on this subject based on the ideXlab platform.
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erythrocyte ion content and dehydration modulate maximal gardos channel activity in KCNN4 v282m hereditary xerocytosis red cells
American Journal of Physiology-cell Physiology, 2019Co-Authors: Alicia Rivera, Immacolata Andolfo, Boris E Shmukler, David H Vandorpe, Achille Iolascon, Natasha M Archer, Estela Shabani, Michael Auerbach, Nelson Hamerschlak, James MortonAbstract:Hereditary xerocytosis (HX) is caused by missense mutations in either the mechanosensitive cation channel PIEZO1 or the Ca2+-activated K+ channel KCNN4. All HX-associated KCNN4 mutants studied to d...
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novel gardos channel mutations linked to dehydrated hereditary stomatocytosis xerocytosis
American Journal of Hematology, 2015Co-Authors: Immacolata Andolfo, Roberta Russo, Antonella Gambale, Francesco Manna, Boris E Shmukler, Giuseppina Vitiello, Gianluca De Rosa, Carlo Brugnara, Seth L AlperAbstract:Dehydrated hereditary stomatocytosis (DHSt) is an autosomal dominant congenital hemolytic anemia with moderate splenomegaly and often compensated hemolysis. Affected red cells are characterized by a nonspecific cation leak of the red cell membrane, reflected in elevated sodium content, decreased potassium content, elevated MCHC and MCV, and decreased osmotic fragility. The majority of symptomatic DHSt cases reported to date have been associated with gain-of-function mutations in the mechanosensitive cation channel gene, PIEZO1. A recent study has identified two families with DHSt associated with a single mutation in the KCNN4 gene encoding the Gardos channel (KCa3.1), the erythroid Ca2+-sensitive K+ channel of intermediate conductance, also expressed in many other cell types. We present here, in the second report of DHSt associated with KCNN4 mutations, two previously undiagnosed DHSt families. Family NA exhibited the same de novo missense mutation as that recently described, suggesting a hot spot codon for DHSt mutations. Family WO carried a novel, inherited missense mutation in the ion transport domain of the channel. The patients' mild hemolytic anemia did not improve post-splenectomy, but splenectomy led to no serious thromboembolic events. We further characterized the expression of KCNN4 in the mutated patients and during erythroid differentiation of CD34+ cells and K562 cells. We also analyzed KCNN4 expression during mouse embryonic development. Am. J. Hematol. 90:921–926, 2015. © 2015 Wiley Periodicals, Inc.
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novel gardos channel mutations linked to dehydrated hereditary stomatocytosis xerocytosis
American Journal of Hematology, 2015Co-Authors: Immacolata Andolfo, Roberta Russo, Antonella Gambale, Francesco Manna, Boris E Shmukler, Giuseppina Vitiello, Gianluca De Rosa, Carlo Brugnara, Seth L AlperAbstract:Dehydrated hereditary stomatocytosis (DHSt) is an autosomal dominant congenital hemolytic anemia with moderate splenomegaly and often compensated hemolysis. Affected red cells are characterized by a nonspecific cation leak of the red cell membrane, reflected in elevated sodium content, decreased potassium content, elevated MCHC and MCV, and decreased osmotic fragility. The majority of symptomatic DHSt cases reported to date have been associated with gain-of-function mutations in the mechanosensitive cation channel gene, PIEZO1. A recent study has identified two families with DHSt associated with a single mutation in the KCNN4 gene encoding the Gardos channel (KCa3.1), the erythroid Ca(2+) -sensitive K(+) channel of intermediate conductance, also expressed in many other cell types. We present here, in the second report of DHSt associated with KCNN4 mutations, two previously undiagnosed DHSt families. Family NA exhibited the same de novo missense mutation as that recently described, suggesting a hot spot codon for DHSt mutations. Family WO carried a novel, inherited missense mutation in the ion transport domain of the channel. The patients' mild hemolytic anemia did not improve post-splenectomy, but splenectomy led to no serious thromboembolic events. We further characterized the expression of KCNN4 in the mutated patients and during erythroid differentiation of CD34+ cells and K562 cells. We also analyzed KCNN4 expression during mouse embryonic development.
Seth L Alper - One of the best experts on this subject based on the ideXlab platform.
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novel gardos channel mutations linked to dehydrated hereditary stomatocytosis xerocytosis
American Journal of Hematology, 2015Co-Authors: Immacolata Andolfo, Roberta Russo, Antonella Gambale, Francesco Manna, Boris E Shmukler, Giuseppina Vitiello, Gianluca De Rosa, Carlo Brugnara, Seth L AlperAbstract:Dehydrated hereditary stomatocytosis (DHSt) is an autosomal dominant congenital hemolytic anemia with moderate splenomegaly and often compensated hemolysis. Affected red cells are characterized by a nonspecific cation leak of the red cell membrane, reflected in elevated sodium content, decreased potassium content, elevated MCHC and MCV, and decreased osmotic fragility. The majority of symptomatic DHSt cases reported to date have been associated with gain-of-function mutations in the mechanosensitive cation channel gene, PIEZO1. A recent study has identified two families with DHSt associated with a single mutation in the KCNN4 gene encoding the Gardos channel (KCa3.1), the erythroid Ca2+-sensitive K+ channel of intermediate conductance, also expressed in many other cell types. We present here, in the second report of DHSt associated with KCNN4 mutations, two previously undiagnosed DHSt families. Family NA exhibited the same de novo missense mutation as that recently described, suggesting a hot spot codon for DHSt mutations. Family WO carried a novel, inherited missense mutation in the ion transport domain of the channel. The patients' mild hemolytic anemia did not improve post-splenectomy, but splenectomy led to no serious thromboembolic events. We further characterized the expression of KCNN4 in the mutated patients and during erythroid differentiation of CD34+ cells and K562 cells. We also analyzed KCNN4 expression during mouse embryonic development. Am. J. Hematol. 90:921–926, 2015. © 2015 Wiley Periodicals, Inc.
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novel gardos channel mutations linked to dehydrated hereditary stomatocytosis xerocytosis
American Journal of Hematology, 2015Co-Authors: Immacolata Andolfo, Roberta Russo, Antonella Gambale, Francesco Manna, Boris E Shmukler, Giuseppina Vitiello, Gianluca De Rosa, Carlo Brugnara, Seth L AlperAbstract:Dehydrated hereditary stomatocytosis (DHSt) is an autosomal dominant congenital hemolytic anemia with moderate splenomegaly and often compensated hemolysis. Affected red cells are characterized by a nonspecific cation leak of the red cell membrane, reflected in elevated sodium content, decreased potassium content, elevated MCHC and MCV, and decreased osmotic fragility. The majority of symptomatic DHSt cases reported to date have been associated with gain-of-function mutations in the mechanosensitive cation channel gene, PIEZO1. A recent study has identified two families with DHSt associated with a single mutation in the KCNN4 gene encoding the Gardos channel (KCa3.1), the erythroid Ca(2+) -sensitive K(+) channel of intermediate conductance, also expressed in many other cell types. We present here, in the second report of DHSt associated with KCNN4 mutations, two previously undiagnosed DHSt families. Family NA exhibited the same de novo missense mutation as that recently described, suggesting a hot spot codon for DHSt mutations. Family WO carried a novel, inherited missense mutation in the ion transport domain of the channel. The patients' mild hemolytic anemia did not improve post-splenectomy, but splenectomy led to no serious thromboembolic events. We further characterized the expression of KCNN4 in the mutated patients and during erythroid differentiation of CD34+ cells and K562 cells. We also analyzed KCNN4 expression during mouse embryonic development.
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physiological roles of the intermediate conductance ca2 activated potassium channel KCNN4
Journal of Biological Chemistry, 2004Co-Authors: Ted Begenisich, Carlo Brugnara, Seth L Alper, Tesuji Nakamoto, Catherine E Ovitt, Keith Nehrke, James E MelvinAbstract:Three broad classes of Ca2+-activated potassium channels are defined by their respective single channel conductances, i.e. the small, intermediate, and large conductance channels, often termed the SK, IK, and BK channels, respectively. SK channels are likely encoded by three genes, Kcnn1–3, whereas IK and most BK channels are most likely products of the KCNN4 and Slo (Kcnma1) genes, respectively. IK channels are prominently expressed in cells of the hematopoietic system and in organs involved in salt and fluid transport, including the colon, lung, and salivary glands. IK channels likely underlie the K+ permeability in red blood cells that is associated with water loss, which is a contributing factor in the pathophysiology of sickle cell disease. IK channels are also involved in the activation of T lymphocytes. The fluid-secreting acinar cells of the parotid gland express both IK and BK channels, raising questions about their particular respective roles. To test the physiological roles of channels encoded by the KCNN4 gene, we constructed a mouse deficient in its expression. KCNN4 null mice were of normal appearance and fertility, their parotid acinar cells expressed no IK channels, and their red blood cells lost K+ permeability. The volume regulation of T lymphocytes and erythrocytes was severely impaired in KCNN4 null mice but was normal in parotid acinar cells. Despite the loss of IK channels, activated fluid secretion from parotid glands was normal. These results confirm that IK channels in red blood cells, T lymphocytes, and parotid acinar cells are indeed encoded by the KCNN4 gene. The role of these channels in water movement and the subsequent volume changes in red blood cells and T lymphocytes is also confirmed. Surprisingly, KCNN4 channels appear to play no required role in fluid secretion and regulatory volume decrease in the parotid gland.
Lyanne C Schlichter - One of the best experts on this subject based on the ideXlab platform.
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il 4 type 1 receptor signaling up regulates KCNN4 expression and increases the kca3 1 current and its contribution to migration of alternative activated microglia
Frontiers in Cellular Neuroscience, 2014Co-Authors: Roger Ferreira, Lyanne C Schlichter, Starlee LivelyAbstract:The Ca2+-activated K+ channel, KCa3.1 (KCNN4/IK1/SK4), contributes to ‘classical’, pro-inflammatory activation of microglia, and KCa3.1 blockers have improved the outcome in several rodent models of CNS damage. For instance, blocking KCa3.1 with TRAM-34 rescued retinal ganglion neurons after optic nerve damage in vivo and, reduced p38 MAP kinase activation, production of reactive oxygen and nitrogen species, and neurotoxicity by microglia in vitro. In pursuing the therapeutic potential of KCa3.1 blockers, it is crucial to assess KCa3.1 contributions to other microglial functions and activation states, especially the IL-4-induced ‘alternative’ activation state that can counteract pro-inflammatory states. We recently found that IL-4 increases microglia migration—a crucial function in the healthy and damaged CNS—and that KCa3.1 contributes to P2Y2 receptor-stimulated migration. Here, we discovered that KCa3.1 is greatly increased in alternative-activated rat microglia and then contributes to an enhanced migratory capacity. IL-4 up-regulated KCNN4 mRNA (by 6 hr) and greatly increased the KCa3.1 current by 1 day, and this required de novo protein synthesis. The increase in current was sustained for at least 6 days. IL-4 increased microglial migration and this was reversed by blocking KCa3.1 with TRAM-34. A panel of inhibitors of signal-transduction mediators was used to analyze contributions of IL-4-related signaling pathways. Induction of KCNN4 mRNA and KCa3.1 current was mediated specifically through IL-4 binding to the type I receptor and, surprisingly, it required JAK3, Ras/MEK/ERK signaling and the transcription factor, AP-1, rather than JAK2, STAT6 or PI3K. The same receptor subtype and pathway were required for the enhanced KCa3.1-dependent migration. In providing the first direct signaling link between an IL-4 receptor, expression and roles of an ion channel, this study also highlights the potential importance of KCa3.1 in alternative-activated microglia.
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microglial sk3 and sk4 currents and activation state are modulated by the neuroprotective drug riluzole
Journal of Neuroimmune Pharmacology, 2013Co-Authors: Lyanne C Schlichter, Roger Ferreira, Starlee LivelyAbstract:Microglia monitor the CNS for ‘danger’ signals after acute injury, such as stroke and trauma, and then undergo complex activation processes. Classical activation of microglia can produce neurotoxic levels of glutamate and immune mediators (e.g., pro-inflammatory cytokines, reactive oxygen and nitrogen species), while alternative activation up-regulates anti-inflammatory molecules and is thought to resolve inflammation and protect the brain. Thus, pharmacological strategies to decrease classical- and/or promote alternative activation are of interest. Here, we assessed actions of the neuroprotective drug, riluzole, on two Ca2+-activated K+ channels in microglia — SK3 (KCa2.3, KCNN3) and SK4 (KCa3.1, KCNN4) — and on classical versus alternative microglial activation. Riluzole is used to treat amyotrophic lateral sclerosis, and is in clinical trials for several other CNS disorders, where it has been presumed to target neurons and reduce glutamate-mediated toxicity. We show that simply elevating intracellular Ca2+ to micromolar levels in whole-cell recordings does not activate SK channels in a cell line derived from primary rat microglia (MLS-9). In intact cells, riluzole raised cytoplasmic Ca2+, but it was marginal (~200 nM) and transient (2 min). Surprisingly then, in whole cell recordings, riluzole rapidly activated SK3 and SK4 channels for as long as it was present, and did not require elevated intracellular Ca2+. We then used primary rat microglia to analyze expression of several activation markers and inflammatory mediators. Riluzole decreased classical LPS-induced activation, and increased some aspects of IL-4-induced alternative activation. These actions on microglia suggest an additional mechanism underlying the neuroprotective actions of riluzole.
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inhibition of the ca2 dependent k channel KCNN4 kca3 1 improves tissue protection and locomotor recovery after spinal cord injury
The Journal of Neuroscience, 2011Co-Authors: Delphine Bouhy, Lyanne C Schlichter, Starlee Lively, Nader Ghasemlou, Adriana Redensek, Khizr I Rathore, Samuel DavidAbstract:Spinal cord injury (SCI) triggers inflammatory responses that involve neutrophils, macrophages/microglia and astrocytes and molecules that potentially cause secondary tissue damage and functional impairment. Here, we assessed the contribution of the calcium-dependent K+ channel KCNN4 (KCa3.1, IK1, SK4) to secondary damage after moderate contusion lesions in the lower thoracic spinal cord of adult mice. Changes in KCNN4 mRNA levels (RT-PCR), KCa3.1 protein expression (Western blots), and cellular expression (immunofluorescence) in the mouse spinal cord were monitored between 1 and 28 d after SCI. KCNN4 mRNA and KCa3.1 protein rapidly increased after SCI; double labeling identified astrocytes as the main cellular source accounting for this upregulation. Locomotor function after SCI, evaluated for 28 d in an open-field test using the Basso Mouse Scale, was improved in a dose-dependent manner by treating mice with a selective inhibitor of KCa3.1 channels, TRAM-34 (triarylmethane-34). Improved locomotor function was accompanied by reduced tissue loss at 28 d and increased neuron and axon sparing. The rescue of tissue by TRAM-34 treatment was preceded by reduced expression of the proinflammatory mediators, tumor necrosis factor-α and interleukin-1β in spinal cord tissue at 12 h after injury, and reduced expression of inducible nitric oxide synthase at 7 d after SCI. In astrocytes in vitro , TRAM-34 inhibited Ca2+ signaling in response to metabotropic purinergic receptor stimulation. These results suggest that blocking the KCa3.1 channel could be a potential therapeutic approach for treating secondary damage after spinal cord injury.
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the ca2 activated sk3 channel is expressed in microglia in the rat striatum and contributes to microglia mediated neurotoxicity in vitro
Journal of Neuroinflammation, 2010Co-Authors: Lyanne C Schlichter, Vikas Kaushal, Vishanthan Sivagnanam, Iska Moxonemre, Catherine VincentAbstract:Background Small-conductance Ca2+ activated K+ channels are expressed in the CNS, where KCNN2/SK2/KCa2.2 and KCNN3/SK3/KCa2.3 help shape the electrical activity of some neurons. The SK3 channel is considered a potential therapeutic target for diseases and disorders involving neuron hyper-excitability but little is known about its expression and roles in non-neuronal cells in either the healthy or damaged CNS. The purpose of this study was to examine expression of KCNN3/SK3 in CNS microglia in vivo and in vitro, and to use an established in vitro model to determine if this channel contributes to the neurotoxic capacity of activated microglia.
Immacolata Andolfo - One of the best experts on this subject based on the ideXlab platform.
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erythrocyte ion content and dehydration modulate maximal gardos channel activity in KCNN4 v282m hereditary xerocytosis red cells
American Journal of Physiology-cell Physiology, 2019Co-Authors: Alicia Rivera, Immacolata Andolfo, Boris E Shmukler, David H Vandorpe, Achille Iolascon, Natasha M Archer, Estela Shabani, Michael Auerbach, Nelson Hamerschlak, James MortonAbstract:Hereditary xerocytosis (HX) is caused by missense mutations in either the mechanosensitive cation channel PIEZO1 or the Ca2+-activated K+ channel KCNN4. All HX-associated KCNN4 mutants studied to d...
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Molecular genetics and pathogenic mechanisms of hereditary anemias due to altered permeability of erythrocyte membrane
2017Co-Authors: Immacolata AndolfoAbstract:Genetic defects of erythrocyte transport proteins cause disorders of red blood cell volume that are characterized by abnormal permeability to the cation and, consequently, by changes in red cell hydration. Within this group of hereditary anemias we focused on familial pseudohyperkalemia and dehydrated hereditary stomatocytosis. The main aims of the project thesis are to study both the molecular genetics and the pathogenic mechanisms of these two disorders. Isolated Familial Pseudohyperkalemia (FP) is a dominant red cell trait characterized by cold-induced ‘passive leak’ of red cell K+ into plasma. The causative gene of this condition is ABCB6, encoding an erythrocyte membrane ABC transporter protein bearing the Langereis blood group antigen system. Dehydrated hereditary stomatocytosis (DHS) is an autosomal dominant congenital hemolytic anemia with moderate splenomegaly and often compensated hemolysis. Red cells are characterized by cation leak of the red cell membrane, reflected in elevated sodium content, decreased potassium content, elevated MCHC and MCV, and decreased osmotic fragility. The majority of symptomatic DHS cases reported to date have been associated with gain-of-function mutations in the mechanosensitive cation channel gene, PIEZO1. Our study started with the recruitment of 97 patients affected by both FP and DHS from 41 unrelated families of Italian and foreign countries. Regarding familial pseudohyperkalemia, analyzing three new families, we reported the first functional characterization of ABCB6 mutants, including homozygous mutation V454A, heterozygous mutation R276W, and compound heterozygous mutations R276W and R723Q. All these mutations are annotated in public databases, suggesting that FP could be common in the general population. Indeed, we identified variant R276W in one of 327 random blood donors (0.3%). Measurement of cation flux demonstrated greater loss of K+ or Rb+ from HEK-293 cells expressing ABCB6 mutants than from cells expressing ABCB6 WT. The R276W/R723Q mutations elicited greater cellular K+ efflux than did the other mutants tested. Regarding dehydrated hereditary stomatocytosis by whole exome sequencing analysis of two previously undiagnosed DHS families we identified the second causative gene of DHS, the KCNN4 gene, encoding the Gardos channel (KCa3.1), the erythroid Ca2+-sensitive K+ channel of intermediate conductance. We characterized the expression of KCNN4 in the mutated patients and during erythroid differentiation of hematopoietic progenitor cell CD34+ and K562 cells. We also analyzed KCNN4 expression during mouse embryonic development. Finally, we demonstrated that the mutations in KCNN4, as for PIEZO1, cause a gain of function, by increasing potassium efflux. Moreover, by analysing the genotype of the patients here collected, we characterized a new interesting mutation in PIEZO1, that is a duplication of two aminoacids localized in the pore of the channel, found in two families with different phenotype. We further analysed the modified effect of an additional PIEZO1 missense variant carried by the family exhibiting the more severe phenotype. We found that the missense variant co-inherited with the duplication cause an augmented potassium efflux. In conclusion, ABCB6 missense mutations in FP erythrocytes show elevated K+ efflux. The patients are present at moderate frequency in the blood donor population. Storage of blood of these patients leads to significantly increased K+ levels, with serious clinical implications for neonates and infants receiving large-volume transfusions of whole blood. Genetic tests for FP could be added to blood donor pre-screening. Further study of ABCB6 function and trafficking could be informative for the study of other pathologies of red blood cell hydration. The identification of KCNN4 mutations in DHS patients supports recent studies that indicate it plays a critical role in normal erythrocyte deformation in the microcirculation and participates in maintenance of erythrocyte volume homeostasis. The characterization of PIEZO1 and KCNN4 mutations in DHS has contributed to the understanding of DHS pathogenesis that will be useful for the prognosis, the management, the follow-up, and the treatment of these patients.
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novel gardos channel mutations linked to dehydrated hereditary stomatocytosis xerocytosis
American Journal of Hematology, 2015Co-Authors: Immacolata Andolfo, Roberta Russo, Antonella Gambale, Francesco Manna, Boris E Shmukler, Giuseppina Vitiello, Gianluca De Rosa, Carlo Brugnara, Seth L AlperAbstract:Dehydrated hereditary stomatocytosis (DHSt) is an autosomal dominant congenital hemolytic anemia with moderate splenomegaly and often compensated hemolysis. Affected red cells are characterized by a nonspecific cation leak of the red cell membrane, reflected in elevated sodium content, decreased potassium content, elevated MCHC and MCV, and decreased osmotic fragility. The majority of symptomatic DHSt cases reported to date have been associated with gain-of-function mutations in the mechanosensitive cation channel gene, PIEZO1. A recent study has identified two families with DHSt associated with a single mutation in the KCNN4 gene encoding the Gardos channel (KCa3.1), the erythroid Ca2+-sensitive K+ channel of intermediate conductance, also expressed in many other cell types. We present here, in the second report of DHSt associated with KCNN4 mutations, two previously undiagnosed DHSt families. Family NA exhibited the same de novo missense mutation as that recently described, suggesting a hot spot codon for DHSt mutations. Family WO carried a novel, inherited missense mutation in the ion transport domain of the channel. The patients' mild hemolytic anemia did not improve post-splenectomy, but splenectomy led to no serious thromboembolic events. We further characterized the expression of KCNN4 in the mutated patients and during erythroid differentiation of CD34+ cells and K562 cells. We also analyzed KCNN4 expression during mouse embryonic development. Am. J. Hematol. 90:921–926, 2015. © 2015 Wiley Periodicals, Inc.
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novel gardos channel mutations linked to dehydrated hereditary stomatocytosis xerocytosis
American Journal of Hematology, 2015Co-Authors: Immacolata Andolfo, Roberta Russo, Antonella Gambale, Francesco Manna, Boris E Shmukler, Giuseppina Vitiello, Gianluca De Rosa, Carlo Brugnara, Seth L AlperAbstract:Dehydrated hereditary stomatocytosis (DHSt) is an autosomal dominant congenital hemolytic anemia with moderate splenomegaly and often compensated hemolysis. Affected red cells are characterized by a nonspecific cation leak of the red cell membrane, reflected in elevated sodium content, decreased potassium content, elevated MCHC and MCV, and decreased osmotic fragility. The majority of symptomatic DHSt cases reported to date have been associated with gain-of-function mutations in the mechanosensitive cation channel gene, PIEZO1. A recent study has identified two families with DHSt associated with a single mutation in the KCNN4 gene encoding the Gardos channel (KCa3.1), the erythroid Ca(2+) -sensitive K(+) channel of intermediate conductance, also expressed in many other cell types. We present here, in the second report of DHSt associated with KCNN4 mutations, two previously undiagnosed DHSt families. Family NA exhibited the same de novo missense mutation as that recently described, suggesting a hot spot codon for DHSt mutations. Family WO carried a novel, inherited missense mutation in the ion transport domain of the channel. The patients' mild hemolytic anemia did not improve post-splenectomy, but splenectomy led to no serious thromboembolic events. We further characterized the expression of KCNN4 in the mutated patients and during erythroid differentiation of CD34+ cells and K562 cells. We also analyzed KCNN4 expression during mouse embryonic development.
Carlo Brugnara - One of the best experts on this subject based on the ideXlab platform.
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novel gardos channel mutations linked to dehydrated hereditary stomatocytosis xerocytosis
American Journal of Hematology, 2015Co-Authors: Immacolata Andolfo, Roberta Russo, Antonella Gambale, Francesco Manna, Boris E Shmukler, Giuseppina Vitiello, Gianluca De Rosa, Carlo Brugnara, Seth L AlperAbstract:Dehydrated hereditary stomatocytosis (DHSt) is an autosomal dominant congenital hemolytic anemia with moderate splenomegaly and often compensated hemolysis. Affected red cells are characterized by a nonspecific cation leak of the red cell membrane, reflected in elevated sodium content, decreased potassium content, elevated MCHC and MCV, and decreased osmotic fragility. The majority of symptomatic DHSt cases reported to date have been associated with gain-of-function mutations in the mechanosensitive cation channel gene, PIEZO1. A recent study has identified two families with DHSt associated with a single mutation in the KCNN4 gene encoding the Gardos channel (KCa3.1), the erythroid Ca2+-sensitive K+ channel of intermediate conductance, also expressed in many other cell types. We present here, in the second report of DHSt associated with KCNN4 mutations, two previously undiagnosed DHSt families. Family NA exhibited the same de novo missense mutation as that recently described, suggesting a hot spot codon for DHSt mutations. Family WO carried a novel, inherited missense mutation in the ion transport domain of the channel. The patients' mild hemolytic anemia did not improve post-splenectomy, but splenectomy led to no serious thromboembolic events. We further characterized the expression of KCNN4 in the mutated patients and during erythroid differentiation of CD34+ cells and K562 cells. We also analyzed KCNN4 expression during mouse embryonic development. Am. J. Hematol. 90:921–926, 2015. © 2015 Wiley Periodicals, Inc.
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novel gardos channel mutations linked to dehydrated hereditary stomatocytosis xerocytosis
American Journal of Hematology, 2015Co-Authors: Immacolata Andolfo, Roberta Russo, Antonella Gambale, Francesco Manna, Boris E Shmukler, Giuseppina Vitiello, Gianluca De Rosa, Carlo Brugnara, Seth L AlperAbstract:Dehydrated hereditary stomatocytosis (DHSt) is an autosomal dominant congenital hemolytic anemia with moderate splenomegaly and often compensated hemolysis. Affected red cells are characterized by a nonspecific cation leak of the red cell membrane, reflected in elevated sodium content, decreased potassium content, elevated MCHC and MCV, and decreased osmotic fragility. The majority of symptomatic DHSt cases reported to date have been associated with gain-of-function mutations in the mechanosensitive cation channel gene, PIEZO1. A recent study has identified two families with DHSt associated with a single mutation in the KCNN4 gene encoding the Gardos channel (KCa3.1), the erythroid Ca(2+) -sensitive K(+) channel of intermediate conductance, also expressed in many other cell types. We present here, in the second report of DHSt associated with KCNN4 mutations, two previously undiagnosed DHSt families. Family NA exhibited the same de novo missense mutation as that recently described, suggesting a hot spot codon for DHSt mutations. Family WO carried a novel, inherited missense mutation in the ion transport domain of the channel. The patients' mild hemolytic anemia did not improve post-splenectomy, but splenectomy led to no serious thromboembolic events. We further characterized the expression of KCNN4 in the mutated patients and during erythroid differentiation of CD34+ cells and K562 cells. We also analyzed KCNN4 expression during mouse embryonic development.
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physiological roles of the intermediate conductance ca2 activated potassium channel KCNN4
Journal of Biological Chemistry, 2004Co-Authors: Ted Begenisich, Carlo Brugnara, Seth L Alper, Tesuji Nakamoto, Catherine E Ovitt, Keith Nehrke, James E MelvinAbstract:Three broad classes of Ca2+-activated potassium channels are defined by their respective single channel conductances, i.e. the small, intermediate, and large conductance channels, often termed the SK, IK, and BK channels, respectively. SK channels are likely encoded by three genes, Kcnn1–3, whereas IK and most BK channels are most likely products of the KCNN4 and Slo (Kcnma1) genes, respectively. IK channels are prominently expressed in cells of the hematopoietic system and in organs involved in salt and fluid transport, including the colon, lung, and salivary glands. IK channels likely underlie the K+ permeability in red blood cells that is associated with water loss, which is a contributing factor in the pathophysiology of sickle cell disease. IK channels are also involved in the activation of T lymphocytes. The fluid-secreting acinar cells of the parotid gland express both IK and BK channels, raising questions about their particular respective roles. To test the physiological roles of channels encoded by the KCNN4 gene, we constructed a mouse deficient in its expression. KCNN4 null mice were of normal appearance and fertility, their parotid acinar cells expressed no IK channels, and their red blood cells lost K+ permeability. The volume regulation of T lymphocytes and erythrocytes was severely impaired in KCNN4 null mice but was normal in parotid acinar cells. Despite the loss of IK channels, activated fluid secretion from parotid glands was normal. These results confirm that IK channels in red blood cells, T lymphocytes, and parotid acinar cells are indeed encoded by the KCNN4 gene. The role of these channels in water movement and the subsequent volume changes in red blood cells and T lymphocytes is also confirmed. Surprisingly, KCNN4 channels appear to play no required role in fluid secretion and regulatory volume decrease in the parotid gland.