Exocytosis of D-aspartate from INS-1E clonal beta cells.
D-Aspartate is present in the central nervous system and various endocrine organs, and modulates their neuroendocrine function. In islets of Langerhans, alpha and beta cells contain D-aspartate. Here we show that INS-1E clonal beta cells contain the highest amount of D-aspartate. Immunohistochemical analysis with specific antibodies against D-aspartate indicated that D-aspartate is co-localized with insulin. Upon the addition of K(+), both D-aspartate and insulin are secreted from the cells in a Ca(2+)-dependent manner. A Ca(2+) ionophore, A23187, also triggers the release of D-aspartate and insulin in the presence of Ca(2+). Bafilomycin A(1), a specific inhibitor of V-ATPase and V-ATPase-linked secondary transport, inhibits the secretion of D-aspartate. These results support the idea that D-aspartate is present in insulin-containing secretory granules and co-secreted with insulin through exocytosis.
Iharada
Masafumi
M
Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
Hiasa
Miki
M
Kobara
Ayumi
A
Moriyama
Yoshinori
Y
D000818:Animals; D001224:Aspartic Acid / Q000032:analysis / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D005089:Exocytosis; D007150:Immunohistochemistry; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar
D007328:Insulin; D001224:Aspartic Acid; D002118:Calcium