G protein subunit alpha (Gα) (Gα)

The G protein subunit alpha (Gα) is the primary signal-transducing component of the heterotrimeric G protein complex and possesses intrinsic GTPase activity [1, 2]. It functions as a molecular switch in signaling pathways initiated by G protein-coupled receptors (GPCRs), the largest superfamily of cell surface receptors [3, 5]. Upon receptor activation, the Gα subunit releases bound GDP in exchange for GTP, leading to its dissociation from the Gβγ dimer and subsequent modulation of downstream effectors such as adenylyl cyclase, phospholipase C, and various ion channels [4, 6, 15]. This signaling is terminated by the intrinsic GTPase function of Gα, which hydrolyzes GTP back to GDP, allowing the reassembly of the inactive heterotrimer [1, 7]. Mutations that impair this GTPase activity result in constitutive activation, which is linked to several diseases, including uveal melanoma (via GNAQ or GNA11 mutations) and endocrine disorders such as McCune-Albright syndrome (via GNAS mutations) [10, 15]. While the majority of clinical therapeutics target the upstream GPCRs, the Gα subunits and their regulators, such as Regulators of G-protein Signaling (RGS) proteins, are increasingly explored as specific therapeutic targets to achieve more precise signaling control [6, 12].

Other names

G alpha subunitHeterotrimeric G protein alpha subunitGuanine nucleotide-binding protein alpha subunitGTP-binding protein alphaG protein-coupled receptor GTPase

Drugs targeting G protein subunits primarily function by inhibiting guanine nucleotide exchange (blocking GDP-GTP transition), preventing the physical interaction between the G protein and its associated GPCR, or by covalently modifying the subunit to either inhibit or constitutively activate its intrinsic GTPase activity [4, 11, 15].