Plays a role as NO/PRKG1-dependent regulator of IP3-induced calcium release; its phosphorylation by PRKG1 inhibits bradykinin and IP3-induced calcium release from intracellular stores. Recruits PRKG1 to the endoplasmic reticulum and may mediate the assembly of PRKG1 and ITPR1 in a macrocomplex. Involved in PRKG1 signaling cascade leading to inhibition of platelet activation and aggregation. Mediates also NO-dependent inhibition of calcium signaling in gastrointestinal smooth muscle contributing to NO-dependent relaxation. Part of cGMP kinase signaling complex at least composed of ACTA2/alpha-actin, CNN1/calponin H1, PLN/phospholamban, PRKG1 and ITPR1 (By similarity). Interacts with PRKG1/cGKI-beta and ITPR1/IP3R type I. Expressed in the colon, rectum, and cultured colonic smooth muscle. Detected in various cancer cell lines. By silencing of the transcription factor BTF3. Phosphorylated by PRKG1/cGKI-beta; Ser-386 showed constitutive phosphorylation in platelets whereas Ser-676 is only phosphorylated in presence of cGMP and nitric oxide (NO); Ser-689 is phosphorylated in resting platelets but increases in presence of cGMP and NO. PRKG1 inhibitor prevents phosphorylation of Ser-676 and Ser-689 in response to NO and cGMP. Unusual initiator. The initiator methionine is coded by a non-canonical CTG leucine codon.