cAMP signaling regulates platelet myosin light chain (MLC) phosphorylation and shape change through targeting the RhoA-Rho kinase-MLC phosphatase signaling pathway

Aburima, Ahmed; Wraith, Katie S.; Raslan, Zaher; Law, Robert; Magwenzi, Simbarashe; Naseem, Khalid M.

Abstract

Cyclic adenosine monophosphate (cAMP)-dependent signaling modulates platelet shape change through unknown mechanisms. We examined the effects of cAMP signaling on platelet contractile machinery. Prostaglandin E1 (PGE1)-mediated inhibition of thrombinstimulated shape change was accompanied by diminished phosphorylation of myosin light chain (MLC). Since thrombin stimulates phospho-MLC through RhoA/Rhoassociated, coiled-coil containing protein kinase (ROCK)-dependent inhibition of MLC phosphatase (MLCP), we examined the effects of cAMP on this pathway. Thrombin stimulated the membrane localization of RhoA and the formation of a signaling complex of RhoA/ROCK2/myosin phosphatase-targeting subunit 1 (MYPT1). This resulted in ROCK-mediated phosphorylation of MYPT1 on threonine 853 (thr853), the disassociation of the catalytic subunit protein phosphatase 1δ (PP1d) from MYPT1 and inhibition of basal MLCP activity. Treatment of platelets with PGE1 prevented thrombin-induced phospho-MYPT1-thr853 in a protein kinase A (PKA)-dependent manner. Examination of the molecular mechanisms revealed that PGE1 induced the phosphorylation of RhoA on serine188 through a pathway requiring cAMP and PKA. This event inhibited the membrane relocalization of RhoA, prevented the association of RhoA with ROCK2 and MYPT1, attenuated the dissociation of PP1δ from MYPT1, and thereby restored basal MLCP activity leading to a decrease in phospho-MLC. These data reveal a new mechanism by which the cAMP-PKA signaling pathway regulates platelet function.

Citation

Aburima, A., Wraith, K. S., Raslan, Z., Law, R., Magwenzi, S., & Naseem, K. M. (2013). cAMP signaling regulates platelet myosin light chain (MLC) phosphorylation and shape change through targeting the RhoA-Rho kinase-MLC phosphatase signaling pathway. Blood, 122(20), 3533-3545. https://doi.org/10.1182/blood-2013-03-487850

• Journal Article Type: Article
• Acceptance Date: Sep 18, 2013
• Online Publication Date: Oct 7, 2013
• Publication Date: Nov 14, 2013
• Deposit Date: Jan 5, 2024
• Journal: Blood
• Print ISSN: 0006-4971
• Electronic ISSN: 1528-0020
• Publisher: American Society of Hematology
• Peer Reviewed: Peer Reviewed
• Volume: 122
• Issue: 20
• Pages: 3533-3545
• DOI: https://doi.org/10.1182/blood-2013-03-487850
• Keywords: Alprostadil; Blood platelets; Cyclic amp; Phosphoric monoester hydrolases; Phosphorylation; Rhoa gtp-binding protein; Signal transduction; Thrombin; Phosphotransferases; Myosin light chains
• Public URL: https://hull-repository.worktribe.com/output/4500783