Requirement of calmodulin-dependent protein kinase II in cyclic ADP-ribose-mediated intracellular Ca2+ mobilization.
Cyclic ADP-ribose (cADPR) is generated in pancreatic islets by glucose stimulation, serving as a second messenger for Ca2+ mobilization from the endoplasmic reticulum for insulin secretion (Takasawa, S., Nata, K., Yonekura, H., and Okamoto, H. (1993) Science 259, 370-373). In the present study, we observed that the addition of calmodulin (CaM) to rat islet microsomes sensitized and activated the cADPR-mediated Ca2+ release. Inhibitors for CaM-dependent protein kinase II (CaM kinase II) completely abolished the glucose-induced insulin secretion as well as the cADPR-mediated and CaM-activated Ca2+ mobilization. Western blot analysis revealed that the microsomes contain the alpha isoform of CaM kinase II but do not contain CaM. When the active 30-kDa chymotryptic fragment of CaM kinase II was added to the microsomes, fully activated cADPR-mediated Ca2+ release was observed in the absence of CaM. These results along with available evidence strongly suggest that CaM kinase II is required to phosphorylate and activate the ryanodine-like receptor, a Ca2+ channel for cADPR as an endogenous activator, for the cADPR-mediated Ca2+ release.
Department of Biochemistry, Tohoku University School of Medicine, Sendai, Japan.
S
S
Takasawa
A
A
Ishida
K
K
Nata
K
K
Nakagawa
N
N
Noguchi
A
A
Tohgo
I
I
Kato
H
H
Yonekura
H
H
Fujisawa
H
H
Okamoto
D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives* / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002147:Calmodulin / Q000494:pharmacology*; D036563:Cyclic ADP-Ribose; D005947:Glucose / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000502:physiology; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D019837:Ryanodine Receptor Calcium Release Channel
D015220:Calcium Channels; D002147:Calmodulin; D007328:Insulin; D009124:Muscle Proteins; D010455:Peptides; D019837:Ryanodine Receptor Calcium Release Channel; C085903:autocamtide-2; D036563:Cyclic ADP-Ribose; D000246:Adenosine Diphosphate Ribose; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D005947:Glucose; D002118:Calcium