Gproteiiniyksiköt

Gproteiiniyksiköt, literally translated from Finnish as “G‑protein units,” refer to the individual subunits that compose heterotrimeric G proteins. A typical heterotrimer consists of alpha (α), beta (β) and gamma (γ) subunits that dissociate upon activation of a G‑protein‑coupled receptor (GPCR). The α‑subunit binds GDP in its inactive state; receptor stimulation causes GDP dissociation and GTP binding, resulting in activation of the α‑subunit and release of the βγ dimer. Both the α‑subunit and the βγ dimer can then interact with downstream effectors such as adenylate cyclase, phospholipase C, ion channels and MAP‑kinase pathways, thereby modulating cellular responses to extracellular signals.

There are more than 20 distinct α‑subunit families (Gs, Gi/o, Gq/11, G12/13 and the recently identified G15/16) and a large repertoire of β and γ subunits, which together provide combinatorial specificity to GPCR signaling. The diversity of Gproteiiniyksiköt underlies the fine‑tuning of processes including vision, olfaction, hormone secretion, neurotransmission and immune responses. Dysregulation of individual G‑protein subunits is associated with various disorders: e.g., loss of Gαi2 function contributes to hypertension, while mutations in Gαs lead to McCune‑Albright syndrome. Pharmaceutical targeting of specific G‑protein subunits is an emerging strategy to modulate GPCR signaling with improved selectivity.