Details

Autor(en) / Beteiligte

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

Titel

Cloning from Insulinoma Cells of Synapsin I Associated with Insulin Secretory Granules

Ist Teil von

• The Journal of biological chemistry, 1999-01, Vol.274 (4), p.2053-2059

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

1999

Quelle

MEDLINE

Beschreibungen/Notizen

• 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.