title: Phosphatidylinositol 3-kinase-dependent translocation of phospholipase Cgamma2 in mouse megakaryocytes is independent of Bruton tyrosine kinase translocation.
abstract: Activation of the collagen receptor glycoprotein VI (GPVI) by a collagen-related peptide (CRP) induces stimulation of platelets and megakaryocytes through the phosphatidylinositol (PI) 3-kinase-dependent pathway leading to activation of Bruton tyrosine kinase (Btk) and phospholipase Cgamma2 (PLCgamma2). Here, we present evidence that both proteins undergo PI 3-kinase-dependent translocation to the plasma membrane on CRP stimulation that is markedly inhibited by wortmannin and LY294002. Translocation of PLCgamma2 but not Btk is also seen in megakaryocytes from X-linked immunodeficiency mice, which have a mutation that reduces the affinity of the pleckstrin homology (PH) domain of Btk for PI 3,4,5-trisphosphate (PI 3,4,5-P3). Activation of PC12 cells by epidermal growth factor (EGF) results in increased PI 3-kinase activity and high PI 3,4,5-P3 levels that trigger translocation of the green fluorescent protein (GFP)-labeled PH of Btk, but not the GFP-labeled PH and tandem Src homology 2 (SH2) domains of PLCgamma2. In contrast to the results with CRP, the G protein-coupled receptor agonist thrombin stimulates PI 3-kinase-independent translocation of Btk but not PLCgamma2. In conclusion, these results demonstrate that in mouse megakaryocytes, CRP leads to PI 3-kinase-dependent translocation of PLCgamma2 and Btk that are independent of one another, whereas thrombin only induces translocation of Btk through a pathway that is independent of PI 3-kinase activity.
authors.affiliation: Department of Pharmacology, University of Oxford, United Kingdom. regis.bobe@pharm.ox.ac.uk
authors.forename: R
authors.initials: R
authors.lastname: Bobe
authors.forename: J I
authors.initials: JI
authors.lastname: Wilde
authors.forename: P
authors.initials: P
authors.lastname: Maschberger
authors.forename: K
authors.initials: K
authors.lastname: Venkateswarlu
authors.forename: P J
authors.initials: PJ
authors.lastname: Cullen
authors.forename: W
authors.initials: W
authors.lastname: Siess
authors.forename: S P
authors.initials: SP
authors.lastname: Watson
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000361:Agammaglobulinemia / Q000201:enzymology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism*; D008533:Megakaryocytes / Q000187:drug effects / Q000201:enzymology*; D051379:Mice; D008817:Mice, Mutant Strains; D008954:Models, Biological; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051966:Phospholipase C gamma; D021381:Protein Transport; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000494:pharmacology; D000072377:Syk Kinase; D013917:Thrombin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000737:chemistry / Q000378:metabolism*; D000077191:Wortmannin; D014960:X Chromosome; D018909:src Homology Domains
chemical_list: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000730:Androstadienes; D002118:Calcium; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051966:Phospholipase C gamma; D011505:Protein-Tyrosine Kinases; D011506:Proteins; D000072377:Syk Kinase; D013917:Thrombin; D010738:Type C Phospholipases; D000077191:Wortmannin; C007105:c1q-binding proteins; C060974:phosphatidylinositol 3,4,5-triphosphate; C000625949:BTK protein, human; C000625951:Btk protein, mouse; C000606896:SYK protein, human; C000606897:Syk protein, mouse