Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present studies were undertaken to determine whether the interaction between cAMP-dependent and insulin-dependent pathways in primary cultures of rat hepatocytes affects biological functions and tyrosine phosphorylation. Quiescent hepatocytes were pretreated with dibutyryl cAMP or cAMP-generating agents such as glucagon, and then treated or not with insulin. Preincubation for 6 h with dibutyryl cAMP or glucagon enhanced the effect of insulin on DNA synthesis, but not the effect of insulin on amino acid transport or glycogen and protein synthesis. Tyrosine phosphorylation of intracellular proteins was determined by immunoblot analysis using an anti-phosphotyrosine antibody. Maximum tyrosine phosphorylation of a 195 kDa protein, which may be a substrate of insulin receptor kinase, of 175-180 kDa proteins, including insulin receptor substrate (IRS)-1, and of 90-95 kDa proteins, including the insulin receptor beta-subunit, was reached within 30 s of incubation with insulin. Pretreatment for about 3 h with dibutyryl cAMP or cAMP-generating agents clearly increased insulin-dependent tyrosine phosphorylation of the 195 kDa protein, but not IRS-1, IRS-2 or the insulin receptor beta-subunit. Because dibutyryl cAMP and cAMP-generating agents did not increase insulin receptor number or its kinase activity, the effect of cAMP on this potentiation of tyrosine phosphorylation is assumed to be exerted at a step distal to insulin receptor kinase activation. The potentiation by cAMP pretreatment of insulin-stimulated tyrosine phosphorylation may in part be secondary to inhibition of phosphotyrosine phosphatase activity, because cAMP pretreatment blunted the effect of Na3VO4 on the net tyrosine phosphorylation of the 195 kDa protein as compared with cells pretreated with no additive. In summary, the interactions between cAMP-dependent and insulin-dependent pathways that lead to augmentation of DNA synthesis appear to parallel the changes in tyrosine phosphorylation. Further studies will be required to determine whether there is a causal relationship between these phenomena.
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PMID:Interaction between cAMP-dependent and insulin-dependent signal pathways in tyrosine phosphorylation in primary cultures of rat hepatocytes. 918 94

Somatostatin (SST), a regulatory peptide, is produced by neuroendocrine, inflammatory, and immune cells in response to ions, nutrients, neuropeptides, neurotransmitters, thyroid and steroid hormones, growth factors, and cytokines. The peptide is released in large amounts from storage pools of secretory cells, or in small amounts from activated immune and inflammatory cells, and acts as an endogenous inhibitory regulator of the secretory and proliferative responses of target cells that are widely distributed in the brain and periphery. These actions are mediated by a family of seven transmembrane (TM) domain G-protein-coupled receptors that comprise five distinct subtypes (termed SSTR1-5) that are endoded by separate genes segregated on different chromosomes. The five receptor subtypes bind the natural SST peptides, SST-14 and SST-28, with low nanomolar affinity. Short synthetic octapeptide and hexapeptide analogs bind well to only three of the subtypes, 2, 3, and 5. Selective nonpeptide agonists with nanomolar affinity have been developed for four of the subtypes (SSTR1, 2, 3, and 4) and putative peptide antagonists for SSTR2 and SSTR5 have been identified. The ligand binding domain for SST ligands is made up of residues in TMs III-VII with a potential contribution by the second extracellular loop. SSTRs are widely expressed in many tissues, frequently as multiple subtypes that coexist in the same cell. The five receptors share common signaling pathways such as the inhibition of adenylyl cyclase, activation of phosphotyrosine phosphatase (PTP), and modulation of mitogen-activated protein kinase (MAPK) through G-protein-dependent mechanisms. Some of the subtypes are also coupled to inward rectifying K(+) channels (SSTR2, 3, 4, 5), to voltage-dependent Ca(2+) channels (SSTR1, 2), a Na(+)/H(+) exchanger (SSTR1), AMPA/kainate glutamate channels (SSTR1, 2), phospholipase C (SSTR2, 5), and phospholipase A(2) (SSTR4). SSTRs block cell secretion by inhibiting intracellular cAMP and Ca(2+) and by a receptor-linked distal effect on exocytosis. Four of the receptors (SSTR1, 2, 4, and 5) induce cell cycle arrest via PTP-dependent modulation of MAPK, associated with induction of the retinoblastoma tumor suppressor protein and p21. In contrast, SSTR3 uniquely triggers PTP-dependent apoptosis accompanied by activation of p53 and the pro-apoptotic protein Bax. SSTR1, 2, 3, and 5 display acute desensitization of adenylyl cyclase coupling. Four of the subtypes (SSTR2, 3, 4, and 5) undergo rapid agonist-dependent endocytosis. SSTR1 fails to be internalized but is instead upregulated at the membrane in response to continued agonist exposure. Among the wide spectrum of SST effects, several biological responses have been identified that display absolute or relative subtype selectivity. These include GH secretion (SSTR2 and 5), insulin secretion (SSTR5), glucagon secretion (SSTR2), and immune responses (SSTR2).
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PMID:Somatostatin and its receptor family. 1043 61