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Titolo:
Rab6 is phosphorylated in thrombin-activated platelets by a protein kinaseC-dependent mechanism: effects on GTP/GDP binding and cellular distribution
Autore:
Fitzgerald, ML; Reed, GL;
Indirizzi:
Harvard Univ, Sch Publ Hlth, Cardiovasc Biol Lab, Boston, MA 02115 USA Harvard Univ Boston MA USA 02115 ardiovasc Biol Lab, Boston, MA 02115 USA
Titolo Testata:
BIOCHEMICAL JOURNAL
, volume: 342, anno: 1999,
parte:, 2
pagine: 353 - 360
SICI:
0264-6021(19990901)342:<353:RIPITP>2.0.ZU;2-N
Fonte:
ISI
Lingua:
ENG
Soggetto:
GDP-DISSOCIATION INHIBITOR; PHORBOL-MYRISTATE ACETATE; MEMBRANE-FUSION; GUANINE-NUCLEOTIDES; GRANULE SECRETION; MOLECULAR-CLONING; EXOCYTOSIS; STIMULATION; TRANSPORT; RECEPTOR;
Keywords:
exocytosis; intracellular signalling; thrombin;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
38
Recensione:
Indirizzi per estratti:
Indirizzo: Reed, GL Harvard Univ, Sch Publ Hlth, Cardiovasc Biol Lab, 677 Huntington Ave, Boston, MA 02115 USA Harvard Univ 677 Huntington Ave Boston MA USA 02115 MA 02115 USA
Citazione:
M.L. Fitzgerald e G.L. Reed, "Rab6 is phosphorylated in thrombin-activated platelets by a protein kinaseC-dependent mechanism: effects on GTP/GDP binding and cellular distribution", BIOCHEM J, 342, 1999, pp. 353-360

Abstract

In platelets and other secretory cells, protein kinase C (PKC) plays a role in exocytosis stimulated by physiological extracellular signals, althoughits linkage to the secretory machinery is poorly understood. We investigated whether Rab6, a GTP-binding protein that fractionates with platelet alpha-granules, may be involved in Linking these processes. We found that Rab6 contains two PKC consensus phosphorylation sites that are evolutionarily conserved. In platelets metabolically labelled with [P-32]P-i, Rab6 phosphorylation was induced by phorbol esters or by thrombin, This phosphorylation was blocked by a specific PKC inhibitor (Ro-31-8220), but not by a p38 mitogen-activated protein kinase inhibitor (PD-169316). Physiological stimulation of platelets caused a PKC-dependent translocation of Rab6 from platelet particulate fractions, nearly doubling the fraction of Rab6 in the cytosol. A human Rab6 isoform (Rab6C) that is preferentially expressed in human platelet RNA was cloned and its phosphorylation by PKC was characterized. Rab6Cincorporated up to 2 mol of [P-32]P-i per mol of active protein. Rab6C bound GDP and GTP with K-d values of 113 +/- 12 and 119 +/- 27 nM respectively, and hydrolysed GTP at a rate of 100 +/- 15 mu mol of GTP/mol of Rab6C permin. PKC phosphorylation of Rab6C increased the affinity for GTP by 3-fold, although it had lesser effects on GDP (1.6-fold). Phosphorylation did notalter the GTPase activity. In summary, thrombin activation of platelets leads to PKC-dependent phosphorylation of Rab6 and a translocation of Rab6 tothe cytosol. We suggest that PKC phosphorylation may be an important mechanism through which Rab functional interactions in vesicle trafficking and secretion can be altered in response to an external stimulus.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 06/06/20 alle ore 11:20:24