Ca2+calmodulin-dependent protein kinase ii and synapsin i-like protein in mouse insulinoma min6 cells

Kazuya Matsumoto, Kohji Fukunaga, Jun Ichi Miyazaki, Motoaki Shichiri, Eishichi Miyamoto

Research output: Contribution to journalArticlepeer-review

55 Citations (Scopus)

Abstract

Ca2+calmodulin-dependent protein kinase II (CaM kinase II) may play a key role in the regulation of insulin secretion. We obtained evidence for the presence of CaM kinase II and its substrate, a 84-kilodalton (kDa) protein, in mouse insulinoma MIN6 cells. CaM kinase II from MIN6 cells has one subunit of 55 kDa, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is autophosphorylated in a Ca2+CaM-dependent manner, and phosphorylates several substrates that serve for rat brain CaM kinase II. In the membrane fraction of MIN6 cells, we identified a 84-kDa protein that was immunoreactive with the antirat brain synapsin I antibody. One-dimensional phosphopeptide mapping by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography revealed the sites of the phosphorylation by cAMP-dependent protein kinase (cAMP kinase) and that by CaM kinase II to be site 1 (10 kDa) and site 2 (30 kDa), respectively, therefore, the same as for rat brain synapsin I. In this context, we tentatively termed it synapsin I-like protein. In 32P-labeled cells, nonfuel insulin secretagogues, such as ionomycin, KCl, and tolbutamide, and a fuel secretagogue, glucose, stimulated autophosphorylation of CaM kinase II and the phosphorylation of synapsin I-like protein. These secretagogues potentiated the Ca(2+)-independent activity of CaM kinase II and secretion of insulin from MIN6 cells. The 84-kDa protein is apparently a newly identified member of the synapsin family. We suggest that CaM kinase II regulates insulin secretion via phosphorylation of synapsin I-like protein.

Original languageEnglish
Pages (from-to)3784-3793
Number of pages10
JournalEndocrinology
Volume136
Issue number9
DOIs
Publication statusPublished - 1995 Sep
Externally publishedYes

ASJC Scopus subject areas

  • Endocrinology

Fingerprint

Dive into the research topics of 'Ca<sup>2+</sup>calmodulin-dependent protein kinase ii and synapsin i-like protein in mouse insulinoma min6 cells'. Together they form a unique fingerprint.

Cite this