Dataset Information

Endogenous substrate proteins for Ca2+-calmodulin-dependent, Ca2+-phospholipid-dependent and cyclic AMP-dependent protein kinases in mouse pancreatic islets.

ABSTRACT: The occurrence of endogenous substrate proteins for Ca2+-dependent protein kinase, augmented by either phospholipid or calmodulin, and for cyclic AMP-dependent protein kinase was examined in homogenates and subcellular fractions of mouse pancreatic islets. Islet protein phosphorylation was enhanced by Ca2+-calmodulin; the major endogenous substrates in the homogenate were two proteins of Mr 53000 and 100000. The Mr-100000 phosphoprotein was localized to a 27000g-supernatant fraction, whereas the Mr-53000 phosphoprotein was present in a 27000g particulate fraction of mouse islets. In the presence of Ca2+, phosphatidylserine stimulated phosphorylation of 15 proteins, of Mr 17000-190000, in a 27000g-supernatant fraction. No effects of Ca2+ plus phosphatidylserine were observed in a 27000g particulate fraction of mouse islets. Examination of cyclic AMP-dependent protein phosphorylation revealed five substrate proteins, of Mr 23000-72000, present in the 27000g supernatant of mouse islets. No common substrates for either the two Ca2+-dependent phosphorylation systems or for the cyclic AMP-dependent and the Ca2+-calmodulin-dependent phosphorylation systems were noted. On the other hand, the actions of the cyclic AMP-sensitive and the Ca2+-phospholipid-sensitive systems may be overlapping, since two common substrates for them were noted in the 27000g-supernatant fraction. The results are consistent with the hypothesis that protein phosphorylation may play a role in the regulation of insulin secretion by Ca2+ and cyclic AMP. The extensive stimulatory effect of phosphatidylserine furthermore suggests that the Ca2+-phospholipid-sensitive protein kinase may prove to be a prominent phosphorylation system in pancreatic islets.

SUBMITTER: Thams P

PROVIDER: S-EPMC1144026 | biostudies-other | 1984 Jul

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:Effects of polyamines on various protein kinases were investigated. It was found that both phospholipid-sensitive Ca2+-dependent protein kinase and myosin light-chain kinase (a calmodulin-sensitive species of Ca2+-dependent protein kinase) were inhibited to different degrees by polyamines, with an approximate order of inhibitory potency of spermine = 1, 12-diaminododecane greater than spermidine = 1, 10-diaminodecane much greater than cadaverine = putrescine. Kinetic analysis revealed that spermine inhibited the phospholipid-sensitive enzyme non-competitively with respect to Ca2+ (Ki = 0.84 mM) and phosphatidylserine (Ki = 0.90 mM); it also inhibited myosin light-chain kinase non-competitively with respect to Ca2+ (Ki = 1.82 mM) and calmodulin (Ki = 2.73 mM). 1, 12-Diaminododecane, in comparison, inhibited the phospholipid-sensitive enzyme competitively with respect to Ca2+ (Ki = 0.45 mM) and phosphatidylserine (Ki = 0.50 mM); it also inhibited myosin light-chain kinase competitively with respect to calmodulin (Ki = 0.63 mM) but non-competitively with respect to Ca2+ (Ki = 1.49 mM). Moreover, spermine (0.5 mM) was found to inhibit markedly phosphatidylserine/Ca2+- and calmodulin/Ca2+-stimulated phosphorylation of endogenous proteins in rat brain particulate fraction. All the polyamines tested were practically without effect on cyclic AMP-dependent and cyclic GMP-dependent protein kinases. Polyarginine, like spermine, was found to be a more selective inhibitor of Ca2+-dependent protein kinases, whereas polyglutamate preferentially inhibited the cyclic nucleotide-dependent enzymes. The present results indicated that, in addition to certain lipophilic compounds (such as trifluoperazine, palmitoylcarnitine, adriamycin and naphthalenesulphonamide) and polypeptides with hydrophobic regions (such as melittin and polymyxin B) previously reported, polycationic compounds (exemplified by polyamines) could also inhibit the two classes of Ca2+-dependent protein kinases requiring either phospholipid or calmodulin as a cofactor. Because of the high cellular concentration (up to 10 mM) and the differential effects of polyamines, it is suggested that spermine, and to smaller extents spermidine and putrescine, may be involved in the regulation of certain Ca2+-dependent protein-phosphorylation systems in vivo.

Dataset Information

Endogenous substrate proteins for Ca2+-calmodulin-dependent, Ca2+-phospholipid-dependent and cyclic AMP-dependent protein kinases in mouse pancreatic islets.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets