Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.17 (CaMKII)
 4,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To assess the role of cAMP in the regulation of autophagy, we examined the effects of cAMP analogues and cAMP-elevating agents on freshly isolated rat hepatocytes, using electroinjected [3H]raffinose as an autophagy probe. Glucagon was found to stimulate, inhibit or have no effect on autophagy, depending on the inclusion of metabolites like pyruvate (which caused ATP depletion and autophagy suppression) and amino acids (a complete mixture that antagonized pyruvate) in the incubation medium. Inhibition was also observed with theophylline, a cAMP-elevating inhibitor of cyclic nucleotide phosphodiesterases, and with the adenylyl cyclase activator deacetylforskolin. At low concentrations of deacetylforskolin, the inhibition could be abolished by amino acids. N6,2'-O-Dibutyryladenosine 3',5'-monophosphate (Bt2-cAMP) strongly inhibited both autophagic sequestration of [3H]raffinose and overall autophagic protein degradation; again, amino acids abolished the autophagy-inhibitory effect of low Bt2-cAMP concentrations. Several other cAMP analogues (8-thiomethyl-cAMP, N6-benzoyl-cAMP, (S)-5,6-dichloro-1-D-ribofuranosylbenzimidazole 3',5'-[thio]monophosphate, (S)-8-bromoadenosine 3',5'-[thio]monophosphate) inhibited autophagy as well. The effect of Bt2-cAMP was rapid, dose-dependent, reversible and did not require concomitant protein synthesis. Neither Bt2-cAMP nor deacetylforskolin reduced intracellular ATP levels or cell viability, ruling out inhibition of autophagy by non-specific cytotoxicity. The autophagy-inhibitory effect of Bt2-cAMP could be substantially antagonized (40-50%) by KT-5720, a specific inhibitor of the cAMP-dependent protein kinase A, and by the nonspecific protein kinase inhibitor K-252a. Somewhat surprisingly, KN-62 and KT-5926, allegedly specific inhibitors of Ca2+/calmodulin-dependent protein kinase II and myosin light chain kinase, respectively, were also Bt2-cAMP-antagonistic. These results suggest that cAMP regulates the early, sequestrational step of hepatocytic autophagy by a highly conditional, dual mechanism, inhibition being predominant under most conditions in freshly isolated hepatocytes, whereas stimulation reportedly predominates in vivo. The effect of cAMP is probably mediated by protein kinase A, but other protein kinases would appear to participate in the regulation of autophagic sequestration as well.
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PMID:Role of cAMP in the regulation of hepatocytic autophagy. 861 61

Whole-cell patch clamp experiments were used to investigate the transduction mechanism of adenosine A(2A) receptors in modulating N-methyl-D-aspartate (NMDA)-induced currents in rat striatal brain slices. The A(2A) receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS 21680) inhibited the NMDA, but not the (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) current in a subset of striatal neurons. Lucifer yellow-filled pipettes in combination with immunostaining of A(2A) receptors were used to identify CGS 21680-sensitive cells as typical medium spiny striatal neurons. Dibutyryl cyclic AMP and the protein kinase A activator Sp-cyclic AMPs, but not the protein kinase A inhibitors Rp-cyclic AMPS or PKI(14 - 24)amide abolished the inhibitory effect of CGS 21680. The phospholipase C inhibitor U-73122, but not the inactive structural analogue U-73343 also interfered with CGS 21680. The activation of protein kinase C by phorbol 12-myristate 13-acetate or the blockade of this enzyme by staurosporine did not alter the effect of CGS 21680. Heparin, an antagonist of inositol 1, 4,5-trisphosphate (InsP(3)) and a more efficient buffering of intracellular Ca(2+) by BAPTA instead of EGTA in the pipette solution, abolished the CGS 21680-induced inhibition. The calmodulin antagonist W-7 and cytochalasin B which enhances actin depolymerization also prevented the effect of CGS 21680; the calmodulin kinase II inhibitors CaM kinase II(281 - 309) and KN-93 but not the inactive structural analogue KN-92 were also effective. The calcineurin inhibitor deltamethrin did not interfere with CGS 21680. It is suggested that the transduction mechanism of A(2A) receptors to inhibit NMDA receptor channels is the phospholipase C/InsP(3)/calmodulin and calmodulin kinase II pathway. The adenylate cyclase/protein kinase A and phospholipase C/protein kinase C pathways do not appear to be involved.
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PMID:Inhibition by adenosine A(2A) receptors of NMDA but not AMPA currents in rat neostriatal neurons. 1080 62