Cloning from insulinoma cells of synapsin I associated with insulin secretory granules

Kazuya Matsumoto, Kenji Ebihara, Hideyuki Yamamoto, Hirotaka Tabuchi, Kohji Fukunaga, Michio Yasunami, Hiroaki Ohkubo, Motoaki Shichiri, Eishichi Miyamoto

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)

Abstract

Synapsin I is a synaptic vesicle-associated protein involved in neurotransmitter release. The functions of this protein are apparently regulated by Ca2+/calmodulin-dependent protein kinase II (CaM kinase II). We reported evidence for CaM kinase II and a synapsin I-like protein present in mouse insulinoma MIN6 cells (Matsumoto, K., Fukunaga, K., Miyazaki, J., Shichiri, M., and Miyamoto, E. (1995) Endocrinology 136, 3784-3793). Phosphorylation of the synapsin I-like protein in these cells correlated with the activation of CaM kinase II and insulin secretion. In the present study, we screened the MIN6 cDNA library with the full-length cDNA probe of rat brain synapsin Ia and obtained seven positive clones; the largest one was then sequenced. The largest open reading frame deduced from the cDNA sequence of 3695 base pairs encoded a polypeptide of 670 amino acids, which exhibited significant sequence similarity to rat synapsin Ib. The cDNA contained the same sequence as the first exon of the mouse synapsin I gene. These results indicate that synapsin Ib is present in MIN6 cells. Synapsin I was expressed in normal rat islets, as determined by reverse transcriptase-polymerase chain reaction analysis. Immunoblot analysis after subcellular fractionation of MIN6 cells demonstrated that synapsin Ib and δ subunit of CaM kinase II co- localized with insulin secretory granules. By analogy concerning regulation of neurotransmitter release, our results suggest that phosphorylation of synapsin I by CaM kinase II may induce the release of insulin from islet cells.

Original languageEnglish
Pages (from-to)2053-2059
Number of pages7
JournalJournal of Biological Chemistry
Volume274
Issue number4
DOIs
Publication statusPublished - 1999 Jan 22
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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