Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.11 (AMPK)
 12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat parathyroid hormone (PTH) stimulates cAMP-dependent protein kinase and protein kinase C activity in the kidney. However, PTH increases intracellular Calcium in primary cultures of proximal tubular cells. We have investigated the possibility that PTH also stimulates Calcium/calmodulin-dependent protein kinase II (CaM kinase II). We have employed the tandem chromatographic column method, using synthetic peptide as a substrate, to measure the renal CaM kinase II activity. PTH (250 nM) stimulated CaM kinase II activity by about 50% after 15 sec., and activity returned to baseline by 2 min. Calmodulin antagonists significantly impaired the stimulatory action of PTH whereas basal levels of CaM kinase II activity were relatively unaffected. This study demonstrates that PTH does activate CaM kinase II in renal tissue, and suggests another pathway for the actions of PTH in the kidney.
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PMID:Effect of parathyroid hormone on rat renal calcium/calmodulin-dependent protein kinase II. 134 39

We found a novel 81-kDa acidic protein (ACAMP-81) in the bovine brain membrane fraction, which bound to calmodulin in a Ca(2+)-dependent manner. The present study reveals physicochemical properties and phosphorylation of this protein with various protein kinases in vitro. The Stokes radius and sedimentation coefficient were calculated to be 52 A and 2.05 S, respectively, suggesting that the structure of ACAMP-81 is highly elongated. Purified Ca2+/phospholipid-dependent protein kinase (protein kinase C), cAMP-dependent protein kinase, and Ca2+/calmodulin-dependent protein kinase II (Ca2+/CaM kinase II) catalyzed the incorporation of 1.46, 0.72, and 0.44 mol of phosphate/mol of ACAMP-81, respectively. The amino acid residues of ACAMP-81 phosphorylated by either protein kinase C or cAMP-dependent protein kinase were almost exclusively on serine. Sequential phosphorylation of ACAMP-81 by cAMP-dependent protein kinase and protein kinase C resulted in the additional incorporation of 1.15 mol of [32P]phosphate into ACAMP-81. Comparison of phosphopeptide maps of ACAMP-81 phosphorylated by each kinase revealed that there are two classes of phosphorylatable polypeptide, one is phosphorylatable by both protein kinases which contained two polypeptides and the others are specific sites for protein kinase C.
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PMID:Phosphorylation of bovine brain 81-kDa acidic calmodulin binding protein (ACAMP-81) in vitro. 165 83

A neuron-specific Ca2+/calmodulin-dependent protein kinase, CaM kinase Gr, phosphorylates selectively a Ras-related GTP-binding protein (Rap-1b) that is enriched in brain tissue. The phosphorylation reaction achieves a stoichiometry of about 1 and involves a serine residue near the carboxyl terminus of the substrate. Both CaM kinase Gr and cAMP-dependent protein kinase, but not CaM kinase II, phosphorylate identical or contiguous serine residues in Rap-1b. The rate of phosphorylation of Rap-1b by CaM kinase Gr is enhanced following autophosphorylation of the protein kinase. Other low molecular weight GTP-binding proteins belonging to the Ras superfamily, including Rab-3A, Rap-2b, and c-Ha-ras p21, are not phosphorylated by CaM kinase Gr. The phosphorylation of Rap-1b itself can be reversed by an endogenous brain phosphoprotein phosphatase. These observations provide a potential connection between a neuronal Ca2(+)-signaling pathway and a specific low molecular weight GTP-binding protein that may regulate neuronal transmembrane signaling, vesicle transport, or neurotransmitter release.
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PMID:Phosphorylation of a Ras-related GTP-binding protein, Rap-1b, by a neuronal Ca2+/calmodulin-dependent protein kinase, CaM kinase Gr. 190 12

1-[N,O-Bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpipera zine (KN-62), a selective inhibitor of rat brain Ca2+/calmodulin-dependent protein kinase II (Ca2+/CaM kinase II) was synthesized and its inhibitory properties in vitro and in vivo were investigated. KN-62 inhibited phosphorylation of exogenous substrate (chicken gizzard myosin 20-kDa light chain) by Ca2+/CaM kinase II with Ki value of 0.9 microM, but no significant effect up to 100 microM on activities of chicken gizzard myosin light chain kinase, rabbit brain protein kinase C, and bovine heart cAMP-dependent protein kinase type II. KN-62 also inhibited the Ca2+/calmodulin-dependent autophosphorylation of both alpha (50 kDa) and beta (60 kDa) subunits of Ca2+/CaM kinase II dose dependently in the presence or absence of exogenous substrate. Kinetic analysis indicated that this inhibitory effect of KN-62 was competitive with respect to calmodulin. However, KN-62 did not inhibit the activity of autophosphorylated Ca2+/CaM kinase II. Moreover, Ca2+/CaM kinase II bound to a KN-62-coupled Sepharose 4B column, but calmodulin did not. These results suggest that KN-62 affects the interaction between calmodulin and Ca2+/CaM kinase II following inhibition of this kinase activity by directly binding to the calmodulin binding site of the enzyme but does not affect the calmodulin-independent activity of already autophosphorylated (activated) enzyme. We examined the effect of KN-62 on cultured PC12 D pheochromocytoma cells. KN-62 suppressed the A23187 (0.5 microM)-induced autophosphorylation of the 53-kDa subunit of Ca2+/CaM kinase in PC12 D cells, which was immunoprecipitated with anti-rat forebrain Ca2+/CaM kinase II polypeptides antibodies coupled to Sepharose 4B, thereby suggesting that KN-62 could inhibit the Ca2+/CaM kinase II activity in vivo.
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PMID:KN-62, 1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazi ne, a specific inhibitor of Ca2+/calmodulin-dependent protein kinase II. 215 22

Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) may play a key role in the regulation of insulin secretion. We obtained evidence for the presence of CaM kinase II and its substrate, a 84-kilodalton (kDa) protein, in mouse insulinoma MIN6 cells. CaM kinase II from MIN6 cells has one subunit of 55 kDa, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is autophosphorylated in a Ca2+/CaM-dependent manner, and phosphorylates several substrates that serve for rat brain CaM kinase II. In the membrane fraction of MIN6 cells, we identified a 84-kDa protein that was immunoreactive with the antirat brain synapsin I antibody. One-dimensional phosphopeptide mapping by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography revealed the sites of the phosphorylation by cAMP-dependent protein kinase (cAMP kinase) and that by CaM kinase II to be site 1 (10 kDa) and site 2 (30 kDa), respectively, therefore, the same as for rat brain synapsin I. In this context, we tentatively termed it synapsin I-like protein. In 32P-labeled cells, nonfuel insulin secretagogues, such as ionomycin, KCl, and tolbutamide, and a fuel secretagogue, glucose, stimulated autophosphorylation of CaM kinase II and the phosphorylation of synapsin I-like protein. These secretagogues potentiated the Ca(2+)-independent activity of CaM kinase II and secretion of insulin from MIN6 cells. The 84-kDa protein is apparently a newly identified member of the synapsin family. We suggest that CaM kinase II regulates insulin secretion via phosphorylation of synapsin I-like protein.
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PMID:Ca2+/calmodulin-dependent protein kinase II and synapsin I-like protein in mouse insulinoma MIN6 cells. 764 85

Type III adenylyl cyclase is stimulated by beta-adrenergic agonists and glucagon in vitro and in vivo, but not by Ca2+ and calmodulin. However, the enzyme is stimulated by Ca2+ and calmodulin in vitro when it is concomitantly activated by the guanyl nucleotide stimulatory protein Gs (Choi, E. J., Xia, Z., and Storm, D. R. (1992a) Biochemistry 31, 6492-6498). Here, we examined regulation of type III adenylyl cyclase by Gs-coupled receptors and intracellular Ca2+ in vivo. Surprisingly, intracellular Ca2+ inhibited hormone-stimulated type III adenylyl cyclase activity. Submicromolar concentrations of intracellular free Ca2+, which stimulated type I adenylyl cyclase, inhibited glucagon- or isoproterenol-stimulated type III adenylyl cyclase. Inhibition of type III adenylyl cyclase by intracellular Ca2+ was not mediated by Gi, cAMP-dependent protein kinase, or protein kinase C. However, an inhibitor of CaM kinases antagonized Ca2+ inhibition of the enzyme, and coexpression of constitutively activated CaM kinase II completely inhibited isoproterenol-stimulated type III adenylyl cyclase activity. We propose that Ca2+ inhibition of type III adenylyl cyclase may serve as a regulatory mechanism to attenuate hormone-stimulated cAMP levels in some tissues.
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PMID:Ca2+ inhibition of type III adenylyl cyclase in vivo. 766 59

We previously reported that the level of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) alpha and beta proteins increases with postnatal age. In the present study, we investigated the developmental changes in whole protein substrates of CaM kinase II as compared with those of cAMP-dependent protein kinase (A-kinase) in the rat forebrain. Protein substrates were phosphorylated with [gamma-33P]ATP, and analysed by two-dimensional gel electrophoresis. More than 50 substrates for CaM kinase II were found in the soluble and particulate fractions. The phosphorylation level of more than 15 substrates increased in the particulate fraction during development. Similarly, that of more than 3 substrates increased in the soluble fraction. Some substrates for A-kinase also increased during development, although some decreased. These findings suggest that the expression of some substrates is regulated during development and that the phosphorylation reaction involves the regulation of neuronal development.
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PMID:Developmental changes of protein substrates of Ca2+/calmodulin-dependent protein kinase II in the rat forebrain. 782 Jun 80

We have demonstrated recently that in cardiac sarcoplasmic reticulum (SR), a membrane-associated Ca2+/calmodulin-dependent protein kinase (CaM kinase) phosphorylates and activates the Ca(2+)-pumping ATPase (Ca(2+)-ATPase) in addition to phosphorylating the previously characterized substrates, phospholamban, and Ca2+ release channel (ryanodine receptor) (Xu, A., Hawkins, C., and Narayanan, N. (1993) J. Biol. Chem. 268, 8394-8397). The present study shows that a CaM kinase regulatory system capable of modulating SR Ca2+ pump activity through direct phosphorylation of the Ca(2+)-ATPase is functional in slow twitch but not fast twitch skeletal muscle. Incubation of SR vesicles isolated from rabbit slow twitch (soleus) and fast twitch (adductor magnus) skeletal muscles in the presence of Ca2+ and calmodulin resulted in phosphorylation of the Ca(2+)-ATPase in slow twitch muscle SR but not in fast twitch muscle SR. Exogenous CaM kinase II, which stimulated phosphorylation of the cardiac and slow twitch muscle SR Ca(2+)-ATPase, failed to phosphorylate fast twitch muscle SR Ca(2+)-ATPase. These observations demonstrate that CaM kinase-catalyzed phosphorylation of the Ca2+ pump is isoform-specific since heart and slow twitch muscle express the same Ca(2+)-ATPase isoform (SERCA2a), which is distinct from that of fast twitch muscle (SERCA1). As in the case of cardiac SR Ca(2+)-ATPase, phosphorylation of the slow twitch muscle SR Ca(2+)-ATPase (occurring at a serine residue) resulted in a 2-fold increase in catalytic activity of the enzyme without alteration in its Ca2+ sensitivity. In addition, Ca2+/calmodulin-dependent prephosphorylation of slow twitch muscle SR resulted in a greater than 2-fold increase in its Ca2+ transport activity. In both cardiac and slow twitch muscle SR, phosphorylation of the Ca(2+)-ATPase by the endogenous CaM kinase occurred rapidly (maximum within 2 min at 37 degrees C), had similar pH optimum (8.5-9.0), temperature optimum (30 degrees C), and calmodulin concentration-dependence (k0.5 50-60 nM). cAMP-dependent protein kinase did not phosphorylate the Ca(2+)-ATPase appreciably in either cardiac or slow twitch muscle SR. These findings suggest a muscle-specific role for the membrane-associated CaM kinase in the modulation of Ca2+ uptake and release functions of the SR. In cardiac and slow twitch muscle, phosphorylation of the SR Ca(2+)-ATPase by CaM kinase might provide a novel mechanism for the modulation of the enzymatic and Ca2+ transport functions of this enzyme.
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PMID:Sarcoplasmic reticulum calcium pump in cardiac and slow twitch skeletal muscle but not fast twitch skeletal muscle undergoes phosphorylation by endogenous and exogenous Ca2+/calmodulin-dependent protein kinase. Characterization of optimal conditions for calcium pump phosphorylation. 798 62

Two size forms of the class B N-type calcium channel alpha 1 subunit were recently identified with CNB1, an antipeptide antibody directed against an intracellular loop of this channel (Westenbroek, R.E., Hell, J.W., Warner, C., Dubel, S.J., Snutch, T.P., and Catterall, W.A. (1992) Neuron 9, 1099-1115). To investigate the biochemical differences between these two size forms, the antibodies CNB3 and CNB4 were raised against peptides with sequences corresponding to the COOH-terminal end of the full-length form. Immunoblot experiments demonstrated that both antibodies specifically recognize the longer form of 250 kDa, indicating that the COOH-terminal regions of the two size forms of the class B N-type channel alpha 1 subunit are different. Phosphorylation experiments with immunopurified calcium channels and different second messenger-activated protein kinases revealed that both the 220- and 250-kDa forms of the class B N-type calcium channel alpha 1 subunit are substrates for cAMP-dependent protein kinase, cGMP-dependent protein kinase, and protein kinase C. These three kinases incorporated approximately 1 mol of phosphate/mol of binding sites for omega-conotoxin (omega-CgTx) GVIA, a ligand specific for the N-type calcium channel, and may regulate the activity of both forms in vivo. In contrast, calcium- and calmodulin-dependent protein kinase II (CaM kinase II) phosphorylated only the long form of the class B N-type calcium channel alpha 1 subunit, with a stoichiometry of 0.5 mol of phosphate/mol of total omega-CgTx GVIA binding sites. Specific phosphorylation of the long form of the class B alpha 1 subunit by CaM kinase II may differentially regulate the function of N-type calcium channels containing different size forms of their alpha 1 subunits in vivo.
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PMID:Differential phosphorylation of two size forms of the N-type calcium channel alpha 1 subunit which have different COOH termini. 812 57

R2D5 is a mouse monoclonal antibody that labels rabbit olfactory receptor neurons. Immunoblot analysis showed that mAb R2D5 recognizes a 22-kD protein with apparent pI of 4.8, which is abundantly contained in the olfactory epithelium and the olfactory bulb. We isolated cDNA for R2D5 antigen and confirmed by Northern analysis and neuronal depletion technique that R2D5 antigen is expressed predominantly, but not exclusively, in olfactory receptor neurons. Analysis of the deduced primary structure revealed that R2D5 antigen consists of 189 amino acids with calculated M(r) of 20,864 and pI of 4.74, has three calcium-binding EF hands, and has possible phosphorylation sites for Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) and cAMP-dependent protein kinase (A kinase). Using the bacterially expressed protein, we directly examined the biochemical properties of R2D5 antigen. R2D5 antigen binds Ca2+ and undergoes a conformational change in a manner similar to calmodulin. R2D5 antigen is phosphorylated in vitro by CaM kinase II and A kinase at different sites, and 1.81 and 0.80 mol of Pi were maximally incorporated per mol of R2D5 antigen by CaM kinase II and A kinase, respectively. Detailed immunohistochemical study showed that R2D5 antigen is also expressed in a variety of ependymal cells in the rabbit central nervous system. Aside from ubiquitous calmodulin, R2D5 antigen is the first identified calcium-binding protein in olfactory receptor neurons that may modulate olfactory signal transduction. Furthermore our results indicate that olfactory receptor neurons and ependymal cells have certain signal transduction components in common, suggesting a novel physiological process in ependymal cells.
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PMID:R2D5 antigen: a calcium-binding phosphoprotein predominantly expressed in olfactory receptor neurons. 822 52


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