Phosphatidylinositol 3,4,5-trisphosphate Regulates Ca(2+) Entry Via Btk in Platelets and Megakaryocytes Without Increasing Phospholipase C Activity
Overview
Molecular Biology
Affiliations
The role of phosphatidylinositol 3,4,5-trisphosphate (PI3,4,5P(3)) and Btk in signalling by the collagen receptor glycoprotein VI was investigated. PI3,4,5P(3) was increased in platelets from mice deficient in the SH2 domain-containing inositol 5-phosphatase (SHIP), in response to collagen related peptide (CRP). Tyrosine phosphorylation and activation of phospholipase Cgamma2 (PLCgamma2) were unaltered in SHIP(-/-) platelets, whereas Btk was heavily tyrosine phosphorylated under basal conditions and maximally phosphorylated by low concentrations of CRP. There was an increase in basal Ca(2+), maximal expression of P-selectin, and potentiation of Ca(2+) and aminophospholipid exposure to CRP in SHIP(-/-) platelets in the presence of Ca(2+) (1 mM). Microinjection of PI3,4, 5P(3) into megakaryocytes caused a 3-fold increase in Ca(2+) in response to CRP, which was absent in X-linked immunodeficiency (Xid) mice, which have a mutation in the PH domain of Btk. There was a corresponding partial reduction in the sustained level of intracellular Ca(2+) in response to CRP in Xid mice but no change in PLC activity. These results demonstrate a novel pathway of Ca(2+) entry that involves PI3,4,5P(3) and Btk, and which is independent of increased PLC activity.
Vav family exchange factors: Potential regulator in atherosclerosis.
Zhang Y, Ren Y, Zhou T, Qian Z, Bao Z Biochem Biophys Rep. 2024; 40:101878.
PMID: 39649800 PMC: 11625217. DOI: 10.1016/j.bbrep.2024.101878.
Markotic A, Omerovic J, Marijan S, Rezic-Muzinic N, culic V Curr Issues Mol Biol. 2024; 46(9):10200-10217.
PMID: 39329960 PMC: 11430773. DOI: 10.3390/cimb46090608.
PI3K Isoform Signalling in Platelets.
Schrottmaier W, Mussbacher M, Salzmann M, Kral-Pointner J, Assinger A Curr Top Microbiol Immunol. 2022; 436:255-285.
PMID: 36243848 DOI: 10.1007/978-3-031-06566-8_11.
Comparison of inhibitory effects of irreversible and reversible Btk inhibitors on platelet function.
Tullemans B, Karel M, Leopold V, Ten Brink M, Baaten C, Maas S EJHaem. 2022; 2(4):685-699.
PMID: 35845214 PMC: 9175945. DOI: 10.1002/jha2.269.
Abivertinib inhibits megakaryocyte differentiation and platelet biogenesis.
Huang J, Huang X, Li Y, Li X, Wang J, Li F Front Med. 2021; 16(3):416-428.
PMID: 34792736 DOI: 10.1007/s11684-021-0838-5.