PRKG1 and schizophrenia: Heterotrimeric G-proteins are composed of the Gα, Gβ, and Gγ subunits, and Gα subunits are further classified into four categories, Gαs, Gαi, Gαq, and Gα12–13, all of which modulate adenylyl cyclase, cAMP, and protein kinases implicated in schizophrenia such as PKA, protein kinase C (PKC), and protein kinase G (PKG) to various degrees [53,54,55].