A Novel Isoform of SK2 Assembles with Other SK Subunits in Mouse Brain
| Autor: | Claudia A. Sailer, John P. Adelman, Timothy Strassmaier, Chris T. Bond, H.-G. Knaus, James Maylie |
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| Rok vydání: | 2005 |
| Předmět: |
Gene isoform
DNA Complementary Small-Conductance Calcium-Activated Potassium Channels Immunoprecipitation Protein subunit Blotting Western Molecular Sequence Data CHO Cells Biology Transfection Hippocampus Biochemistry Mice Potassium Channels Calcium-Activated Cricetinae Complementary DNA Animals Protein Isoforms Homomeric Amino Acid Sequence Cysteine Disulfides Molecular Biology Cerebral Cortex Dose-Response Relationship Drug Sequence Homology Amino Acid Cell Membrane Wild type Brain Cell Biology Immunohistochemistry Molecular biology Protein Structure Tertiary Cell biology Electrophysiology Membrane protein COS Cells Calcium Heterologous expression |
| Zdroj: | Journal of Biological Chemistry. 280:21231-21236 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m413125200 |
| Popis: | The SK2 subtype of small conductance Ca2+-activated K+ channels is widely distributed throughout the central nervous system and modulates neuronal excitability by contributing to the afterhyperpolarization that follows an action potential. Western blots of brain membrane proteins prepared from wild type and SK2-null mice reveal two isoforms of SK2, a 49-kDa band corresponding to the previously reported SK2 protein (SK2-S) and a novel 78-kDa form. Complementary DNA clones from brain and Western blots probed with an antibody specific for the longer form, SK2-L, identified the larger molecular weight isoform as an N-terminally extended SK2 protein. The N-terminal extension of SK2-L is cysteine-rich and mediates disulfide bond formation between SK2-L subunits or with heterologous proteins. Immunohistochemistry revealed that in brain SK2-L and SK2-S are expressed in similar but not identical patterns. Heterologous expression of SK2-L results in functional homomeric channels with Ca2+ sensitivity similar to that of SK2-S, consistent with their shared core and intracellular C-terminal domains. In contrast to the diffuse, uniform surface distribution of SK2-S, SK2-L channels cluster into sharply defined, distinct puncta suggesting that the extended cysteine-rich N-terminal domain mediates this process. Immunoprecipitations from transfected cells and mouse brain demonstrate that SK2-L co-assembles with the other SK subunits. Taken together, the results show that the SK2 gene encodes two subunit proteins and suggest that native SK2-L subunits may preferentially partition into heteromeric channel complexes with other SK subunits. |
| Databáze: | OpenAIRE |
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