A role for PKCtheta in outside-in alpha(IIb)beta3 signaling.
Fibrinogen binding to platelets triggers alpha(IIb)beta3-dependent outside-in signals that promote actin rearrangements and cell spreading. Studies with chemical inhibitors or activators have implicated protein kinase C (PKC) in alpha(IIb)beta3 function. However, the role of individual PKC isoforms is poorly understood. Biochemical and genetic approaches were used to determine whether PKCtheta is involved in alpha(IIb)beta3 signaling. PKCtheta was constitutively associated with alpha(IIb)beta3 in human and murine platelets. Fibrinogen binding to alpha(IIb)beta3 stimulated the association of PKCtheta with tyrosine kinases Btk and Syk, and tyrosine phosphorylation of PKCtheta, Btk and the actin regulator, Wiskott-Aldrich syndrome protein (WASP). Mouse platelets deficient in PKCtheta or Btk failed to spread on fibrinogen. Furthermore, PKCtheta was required for phosphorylation of WASP-interacting protein on Ser-488, an event that has been linked to WASP activation of the Arp2/3 complex and actin polymerization in lymphocytes. Neither PKCtheta nor Btk were required for agonist-induced inside-out signaling and fibrinogen binding to alpha(IIb)beta3. Thus, PKCtheta is a newly identified, essential member of a dynamic outside-in signaling complex that includes Btk and that couples alpha(IIb)beta3 to the actin cytoskeleton.
Soriani
A
A
Division of Hematology-Oncology, Department of Medicine, University of California San Diego, La Jolla, CA, USA. alessandra.soriani@uniroma1.it
Moran
B
B
de Virgilio
M
M
Kawakami
T
T
Altman
A
A
Lowell
C
C
Eto
K
K
Shattil
S J
SJ
D000199:Actins / Q000378:metabolism; D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D048430:Cell Shape; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005340:Fibrinogen / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D011493:Protein Kinase C / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D000072377:Syk Kinase; D014443:Tyrosine / Q000378:metabolism; D051316:Wiskott-Aldrich Syndrome Protein / Q000378:metabolism
D000199:Actins; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; C495768:Was protein, mouse; D051316:Wiskott-Aldrich Syndrome Protein; D014443:Tyrosine; D005340:Fibrinogen; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; C489593:Prkcq protein, mouse; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta