VPB0409 - GRK2 regulates ADP signaling in platelets

Sunday, July 10, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: Virtual

Presenting Author(s)

Xuefei Zhao, MS

PhD student
Thomas Jefferson University
Philadelphia, Pennsylvania, United States

Co-Author(s)

MC

Matthew Cooper

Student
Thomas Jefferson University
Philadelphia, Pennsylvania, United States
YY

Yanki Yarman

MD/PhD student
Thomas Jefferson University
Philadelphia, Pennsylvania, United States
JM

James V. Michael

Research Assistant professor
Thomas Jefferson University
Philadelphia, Pennsylvania, United States
KC

Kurt Chuprun

Researcher
Temple University
Philadelphia, Pennsylvania, United States
WK

Walter Koch

Professor
Temple University
Philadelphia, Pennsylvania, United States
Steven E McKenzie, MD, PhD

Professor
Thomas Jefferson University
Philadelphia, Pennsylvania, United States
MT

Maurizio Tomaiuolo

Researcher
Thomas Jefferson University
Philadelphia, Pennsylvania, United States
TS

Timothy J. Stalker

Assistant professor
Thomas Jefferson University
Philadelphia, Pennsylvania, United States
LZ

Li Zhu

Professor
Soochow University
Soochow, Jiangsu, China (People's Republic)
PM

Peisong Ma

Assitant Professor
Thomas Jefferson University
Philadelphia, Pennsylvania, United States

Background: The critical role of GRK2 in regulating cardiac function has been well documented for over three decades. Therefore, targeting GRK2 has been extensively studied as a novel approach to treat cardiovascular disease. However, little is known about its role in hemostasis and thrombosis.

Aims: To investigate the function of GRK2 during platelet activation and how GRK2 regulates the hemostatic response to injury.

Methods: We took advantage of using a megakaryocyte/platelet-specific GRK2-/- mouse model. We examined the impact of GRK2 deficiency on platelet activation and platelet accumulation at the site of vascular injury.

Results: Deletion of GRK2 in mouse platelets causes increased platelet accumulation following laser-induced injury in cremaster muscle arterioles, particularly in the shell region of thrombi. GRK2-/- platelets have increased platelet aggregation in response to ADP, but not to PAR4 receptor agonist, TxA2, or convulxin. Furthermore, GRK2-/- platelets retain the ability to aggregate in response to ADP re-stimulation, indicating that GRK2 contributes to ADP receptor desensitization. Underlying these changes in GRK2-/- platelets is an increase in Ca2+ mobilization, RAP1 activation, and Akt phosphorylation in response to ADP, and an attenuated rise of cAMP levels in response to ADP in the presence of prostaglandin I2. Cangrelor treatment eliminates the phenotypic difference in platelet accumulation between WT and GRK2-/- mice at the site of injury. In addition, absence of GRK2 increases ADP-induced pulmonary thromboembolism. Pharmacologic inhibition of GRK2 activity in human platelets increases platelet activation in response to ADP. Finally, we show that GRK2 binds to endogenous Gβγ subunits during platelet activation.

Conclusion(s): Taken together, we have demonstrated for the first time that 1) GRK2 regulates ADP signaling via P2Y1 and P2Y12, 2) GRK2 interacts with Gβγ and functions as a signaling hub in platelets for fine-tuning GPCR signaling, and 3) maintaining GRK2 activity in platelets may be beneficial for prevention of thrombotic diseases.