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The inositol 1,4,5-trisphosphate receptor.
K Mikoshiba1, T Furuichi, A Miyawaki
1Institute for Protein Research, Osaka University, Japan.
Ciba Foundation Symposium
|January 1, 1992
Summary
Inositol 1,4,5-trisphosphate (InsP3) receptor, identified as P400 protein, mediates physiological calcium (Ca2+) release. Novel subtypes of this InsP3 receptor were discovered, showing tissue-specific and developmental expression.
Area of Science:
- Cell Biology
- Molecular Biology
- Neuroscience
Background:
- Inositol 1,4,5-trisphosphate (InsP3) acts as a crucial second messenger.
- InsP3 regulates intracellular calcium (Ca2+) release from storage sites.
- The InsP3 receptor's identity and function were under investigation.
Purpose of the Study:
- To identify the InsP3 receptor and elucidate its role in Ca2+ signaling.
- To characterize the InsP3 receptor's binding properties and cellular localization.
- To investigate the heterogeneity and expression patterns of the InsP3 receptor.
Main Methods:
- Purification and cDNA cloning of the InsP3 receptor.
- Generation of transfected L-fibroblast cell lines.
- Calcium (Ca2+) release assays and electrophysiological recordings.
- Immunogold labeling and cross-linking experiments.
- Polymerase chain reaction (PCR) for subtype analysis.
Main Results:
- The InsP3 receptor was found to be identical to the P400 protein, enriched in Purkinje cells.
- Transfected cells exhibited InsP3-induced Ca2+ release, confirming receptor function.
- The receptor localizes to the endoplasmic reticulum and nuclear membrane.
- Cross-linking revealed the receptor forms a homotetramer.
- Novel, tissue- and developmentally-specific InsP3 receptor subtypes were identified.
Conclusions:
- The InsP3 receptor (P400 protein) is essential for physiological Ca2+ release.
- The N-terminal region is critical for InsP3 binding and conserved across species.
- Heterogeneity in InsP3 receptor subtypes suggests complex regulatory mechanisms in Ca2+ signaling.