TY - JOUR
T1 - Rapid glucose sensing by protein kinase A for insulin exocytosis in mouse pancreatic islets
AU - Hatakeyama, Hiroyasu
AU - Kishimoto, Takuya
AU - Nemoto, Tomomi
AU - Kasai, Haruo
AU - Takahashi, Noriko
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2006/1
Y1 - 2006/1
N2 - The role of protein kinase A (PKA) in insulin exocytosis was investigated with the use of two-photon excitation imaging of mouse islets of Langerhans. Inhibitors of PKA selectively reduced the number of exocytic events during the initial period (< 250 s) of the first phase of glucose-induced exocytosis (GIE), without affecting the second phase, in intact islets or small clusters of islet cells. The PKA inhibitors did not reduce the extent of the glucose-induced increase in [Ca2+]i. The actions of glucose and PKA in Ca2+ -induced insulin exocytosis (CIE) triggered by photolysis of a caged-Ca2+ compound, which resulted in large increases in [Ca2+]i and thereby bypassed the ATP-sensitive K+ channel-dependent mechanism of glucose sensing, were therefore studied. A high concentration (20mM) of glucose potentiated CIE within 1 min, and this effect was blocked by inhibitors of PKA. This PKA-dependent action of glucose required glucose metabolism, given that increasing the intracellular concentration of cAMP by treatment with forskolin potentiated CIE only at the high glucose concentration. Finally, PKA appeared to reduce the frequency of 'kiss-and-run' exocytic events and to promote full-fusion events during GIE. These data indicate that a PKA-dependentmechanism of glucose sensing,which is operative even at the basal level of PKA activity, plays an important role specifically in the first phase of GIE, and they suggest that the action of PKA is mediated at the level of the fusion reaction.
AB - The role of protein kinase A (PKA) in insulin exocytosis was investigated with the use of two-photon excitation imaging of mouse islets of Langerhans. Inhibitors of PKA selectively reduced the number of exocytic events during the initial period (< 250 s) of the first phase of glucose-induced exocytosis (GIE), without affecting the second phase, in intact islets or small clusters of islet cells. The PKA inhibitors did not reduce the extent of the glucose-induced increase in [Ca2+]i. The actions of glucose and PKA in Ca2+ -induced insulin exocytosis (CIE) triggered by photolysis of a caged-Ca2+ compound, which resulted in large increases in [Ca2+]i and thereby bypassed the ATP-sensitive K+ channel-dependent mechanism of glucose sensing, were therefore studied. A high concentration (20mM) of glucose potentiated CIE within 1 min, and this effect was blocked by inhibitors of PKA. This PKA-dependent action of glucose required glucose metabolism, given that increasing the intracellular concentration of cAMP by treatment with forskolin potentiated CIE only at the high glucose concentration. Finally, PKA appeared to reduce the frequency of 'kiss-and-run' exocytic events and to promote full-fusion events during GIE. These data indicate that a PKA-dependentmechanism of glucose sensing,which is operative even at the basal level of PKA activity, plays an important role specifically in the first phase of GIE, and they suggest that the action of PKA is mediated at the level of the fusion reaction.
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U2 - 10.1113/jphysiol.2005.096560
DO - 10.1113/jphysiol.2005.096560
M3 - Article
C2 - 16284079
AN - SCOPUS:33644538464
VL - 570
SP - 271
EP - 282
JO - Journal of Physiology
JF - Journal of Physiology
SN - 0022-3751
IS - 2
ER -