Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Serine-specific and threonine-specific casein kinase activities have been identified in a Golgi-enriched membrane fraction isolated from the lactating guinea-pig mammary gland. The serine-specific casein kinase has been purified 2000-fold by affinity chromatography on ATP-agarose. The enzyme has an estimated Mr of 100000 as determined by sucrose gradient centrifugation and phosphorylates the serine residues of dephosphorylated guinea-pig caseins A and B in a qualitatively and quantitatively identical manner to caseins A and B secreted by lactating mammary gland explants in organ culture. The enzyme also phosphorylates casein C at serine, but not threonine residues. Studies on the relative location of the enzyme within a Golgi-enriched membrane fraction show that it is an integral component of the membrane, either in the form of a transmembrane protein or exposed on the luminal side of the membrane. Although casein kinase activity is not associated with the endoplasmic reticulum, it remains to be proven whether it is truly a Golgi enzyme, since analysis of subcellular membrane components fractionated by sucrose gradient centrifugation shows that the particulate protein kinase activity of the lactating mammary gland does not cosediment with galactosyl transferase, possibly a reflection of the heterogeneous nature of mammary gland Golgi apparatus. It seems likely that the serine-specific casein kinase activity described is responsible for the phosphorylation of caseins in the lactating guinea-pig mammary gland, and that this occurs after the sequestration of processed but unphosphorylated caseins within the lumen of the endoplasmic reticulum.
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PMID:Characterisation of a membrane-bound serine-specific casein kinase isolated from lactating guinea-pig mammary gland. 680 32

We describe a potential regulatory mechanism for the transmembrane protein-tyrosine phosphatase CD45. Phosphorylation on both tyrosine and serine residues in vitro results in an activation of CD45 specifically toward one artificial substrate but not another. The activation of these kinases appears to be order dependent, as it is enhanced when phosphorylation of tyrosine precedes that of serine but phosphorylation in the reverse order yields no activation. Any of four protein-tyrosine kinases tested, in combination with the protein-serine/threonine kinase, casein kinase II, was capable of mediating this activation in vitro. The time course of phosphorylation of CD45 in response to T-cell activation is consistent with the possibility that this regulatory mechanism is utilized in vivo.
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PMID:Protein-tyrosine phosphatase activity of CD45 is activated by sequential phosphorylation by two kinases. 751 65

We evaluated in Jurkat T cells the time-dependent responses of Fyn, Lck, Syk, and Zap following antibody-mediated cross-linking of the T cell antigen receptor. Our results show that the protein kinase activities of Fyn and Lck were activated within seconds of receptor cross-linking. Fyn activity, as measured by autophosphorylation and tyrosine phosphorylation of an exogenous substrate, was maximal 5 s to 1 min following receptor cross-linking. Lck was also found to be activated within 5 s of antigen receptor cross-linking but differed from Fyn in that Lck activity was elevated for at least 30 min. Syk and Zap protein kinase activities were found to peak between 5 and 10 min following receptor cross-linking, returning to approximately basal activity levels by 60 min. The protein kinase activities of both Syk and Zap were found to parallel their reactivity in immunoblotting experiments with anti-phosphotyrosine antibodies. Both Syk and Zap were found to associate with the tyrosine-phosphorylated zeta subunit of the T cell antigen receptor. These observations imply that T cell antigen receptor signal transduction involves the activation of multiple members of at least two different families of non-transmembrane protein tyrosine kinases.
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PMID:Temporal regulation of non-transmembrane protein tyrosine kinase enzyme activity following T cell antigen receptor engagement. 752 30

The granulocyte activation Ags, CD66a, CD66b, CD66c, and CD66d, are expressed at low levels on resting blood granulocytes, but their surface expression is up-regulated following stimulation. CD66a, in contrast to CD66b and CD66c which are anchored to the membrane via a glycosyl-phosphatidylinositol linkage, is a transmembrane protein with a cytoplasmic domain. We have previously reported that CD66a is phosphorylated in human neutrophils, largely on tyrosine, with a lower level of phosphoserine. We have now found that CD66a undergoes a rapid increase in phosphorylation following stimulation with FMLP, platelet-activating factor, and 12-O-tetradecanoyl-phorbol-13-acetate. This increase in phosphorylation was transient, with maximal phosphorylation observed by 1 min and a return to base line by 5 min following stimulation. Protein kinase activity was detected in neutrophils associated with CD66a, CD66b, and CD66c. Most of the protein kinase activity associated with these Ags was tyrosine kinase activity, with a lesser amount of threonine and serine kinase activities. Lyn and Hck accounted for much of the associated tyrosine kinase activity. The data suggest that phosphorylation of CD66a on tyrosine by an associated tyrosine kinase may play a role in the function of CD66a. In addition, associated tyrosine kinase activity may play a role in signal transduction from CD66a, CD66b, and CD66c to regulate other cell functions.
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PMID:CD66 family members are associated with tyrosine kinase activity in human neutrophils. 759 54

Serum-free aggregating rat brain cell cultures provide sufficient cell surface and paracrine interactions between neurons and glial cells for compact myelination. We are interested in the part played in these signalling pathways by protein kinases and have used a PCR cDNA cloning approach to catalogue the protein kinase genes expressed by these cultures. 8 transmembrane protein kinases were identified: IGF1-R, trk B, bFGF-R, c-met, Tyro2, Tyro1, Tyro4 and a novel eck-related gene. The first 4 are receptors for ligands with known trophic functions. Tyro2 is a novel gene related to the EGF-R. The latter 3 belong to the eck gene family of more than 8 highly related putative receptors for, as yet, unknown ligands. 8 cDNAs for intracellular protein kinases were also isolated including 3 novel genes. Ongoing studies are investigating whether these proteins contribute to myelination and/or could be used as therapeutic targets in demyelinating diseases.
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PMID:Protein kinases expressed in aggregating brain cell cultures during myelination. 768 71

We recently identified a novel 8-kDa transmembrane protein, Mat-8, that is expressed in a subset of murine breast tumors. We have now cloned a cDNA encoding the human version of Mat-8 and show that it is expressed both in primary human breast tumors and in human breast tumor cell lines. The extracellular and transmembrane domains of Mat-8 are homologous to those of phospholemman (PLM), the major plasmalemmal substrate for cAMP-dependent protein kinase and protein kinase C in several different tissues. PLM, which induces chloride currents when expressed in Xenopus oocytes, contains consensus phosphorylation sites for both cAMP-dependent protein kinase A and protein kinase C in its cytoplasmic domain. In contrast, the cytoplasmic domain of Mat-8 contains no such consensus phosphorylation sites and is, in fact, unrelated to the cytoplasmic domain of PLM. RNA blot analysis reveals that Mat-8 and PLM exhibit distinct tissue-specific patterns of expression. We show that expression of Mat-8 in Xenopus oocytes induces hyperpolarization-activated chloride currents similar to those induced by PLM expression. These findings suggest that Mat-8 and PLM, the products of distinct genes, are related proteins that serve as Cl- channels or Cl- channel regulators but have different roles in cell and organ physiology.
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PMID:Mat-8, a novel phospholemman-like protein expressed in human breast tumors, induces a chloride conductance in Xenopus oocytes. 783 47

The earliest physical sign of differentiation in the Drosophila retina is the passage of the morphogenetic furrow across the epithelium of the eye disc. Secreted factors encoded by hedgehog (hh) and decapentaplegic (dpp) have been implicated in propagation of the furrow and the subsequent initiation of photoreceptor differentiation. The morphogenetic furrow initiates at the posterior edge of the third larval instar eye imaginal disc. Its continued progression towards the anterior is believed to depend upon secretion of Hh protein by the differentiating clusters of photoreceptors that emerge posterior to the moving furrow. This progression is marked by the initiation of expression of the transforming growth factor-beta homologue Dpp in cells entering the furrow anteriorly, and loss of dpp expression in cells emerging posteriorly. Although the transmembrane protein encoded by the patched gene has been genetically implicated as the Hh receptor, the intercellular signalling pathways involved in these inductive processes remain uncharacterized. Here we show that the catalytic subunit of cyclic AMP-dependent protein kinase A (Pka-C1) is required for the correct spatial regulation of dpp expression during eye development. Loss of Pka-C1 function is sufficient to produce an ectopic morphogenetic wave marked by premature ectopic photoreceptor differentiation and non-autonomous propagation of dpp expression. Our results indicate that Pka-C1 lies in a signalling pathway that controls the orderly temporal progression of differentiation across the eye imaginal disc.
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PMID:Regulation of furrow progression in the Drosophila eye by cAMP-dependent protein kinase A. 785 37

Activin type II receptors are transmembrane protein-serine/threonine kinases. By using a reverse-transcription PCR assay to screen for protein kinase sequences, we isolated a cDNA clone, activin X1 receptor, from rat brain that encodes a 55-kDa transmembrane protein-serine kinase which is structurally related to other receptors in this kinase subfamily. The predicted protein consists of 509 amino acids, and the kinase domain shows 40% and 37% identity to the activin and transforming growth factor beta type II receptors, respectively. No activin-binding was observed when activin X1 receptor was expressed alone in COS-M6 cells; however, coexpression with type II activin receptors gave rise to a 68-kDa affinity-labeled complex in addition to the 85-kDa type II receptor complex. The size of this cross-linked band is consistent with the size of the type I activin receptor; furthermore, activin X1 receptor associated with type II receptors, as judged by coimmunoprecipitation with type II receptor antibodies. These data suggest that activin X1 receptor can serve as an activin type I receptor and that the diverse biological effects of activins may be mediated by a complex formed by the interaction of two transmembrane protein-serine kinases.
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PMID:Cloning and characterization of a transmembrane serine kinase that acts as an activin type I receptor. 824 34

The B-cell antigen receptor is composed of membrane immunoglobulin sheathed by an alpha/beta heterodimer. The complex is noncovalently associated with protein kinase activity, and crosslinking of the receptor leads to capping and transmembrane signaling. Here we show that the sheath is not necessary either for this capping or for the association of membrane immunoglobulin with the detergent-insoluble cytoskeletal fraction that occurs following crosslinking. It is also not required for association of membrane immunoglobulin with a casein-kinase-like serine/threonine kinase. The sheath is essential, however, for transmembrane signaling. Provision of just the cytoplasmic domain of the beta sheath polypeptide to a mutant, unsheathed IgM molecule was sufficient to restore full signaling capability as judged by the phosphorylation of a variety of cellular proteins, including the B-cell-specific transmembrane protein CD22. This signaling was destroyed by mutating one of the tyrosines in the beta cytoplasmic domain. These results not only suggest that receptor signaling is mediated through phosphorylation of the tyrosines in the sheath's cytoplasmic domains but, together with previous work, indicate that different motifs within the sheath mediate presentation and signaling.
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PMID:The alpha/beta sheath and its cytoplasmic tyrosines are required for signaling by the B-cell antigen receptor but not for capping or for serine/threonine-kinase recruitment. 829 May 50

In eukaryotic cells, the accumulation of unfolded proteins in the endoplasmic reticulum (ER) triggers a signaling pathway from the ER to the nucleus. Several yeast mutants defective in this pathway map to the ERN1 gene, which protects cells from lethal consequences of stress by signaling for increased expression of BiP and other ER proteins. ERN1 encodes a 1115 amino acid transmembrane protein (Ern1p) whose glycosylated N-terminal portion is located inside microsomes and whose cytoplasmic C-terminal portion carries an essential protein kinase activity. We postulate that Ern1p is the proximal sensor of events in the ER and that binding of ligand causes transduction of information across the ER membrane, leading to activation of a specific set of transcription factors.
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PMID:A transmembrane protein with a cdc2+/CDC28-related kinase activity is required for signaling from the ER to the nucleus. 835 94


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