Protein Kinase, cGMP Dependent Type I (PRKG1)

Two main forms of cGK have been identified: a soluble form designated type I and an intrinsic membrane-bound form designated type II.

Prkg1 knockout mice showed impaired platelet responses to VWF or low doses of thrombin and prolonged bleeding time. Human platelet aggregation induced by VWF or low-dose thrombin was inhibited by PRKG1 inhibitors but enhanced by cGMP. Furthermore, a cGMP-enhancing agent, sildenafil, promoted VWF- or thrombin-induced platelet aggregation. The cGMP-stimulated platelet responses were biphasic, consisting of an initial transient stimulatory response that promoted platelet aggregation and a subsequent inhibitory response that limited the size of thrombi.