Guanylate cyclase-activating protein 1 (GCAP1)

Guanylate cyclase-activating protein 1 (GCAP1) is a neuronal calcium sensor protein primarily expressed in rod and cone photoreceptors of the retina. It detects changes in intracellular Ca²⁺ concentration and acts as a molecular switch: at low Ca²⁺ (light-adapted state), GCAP1 binds Mg²⁺ and activates retinal guanylate cyclase (RetGC), promoting the synthesis of cyclic GMP necessary for photoresponse recovery; at high Ca²⁺ (dark state), GCAP1 inhibits RetGC to maintain cGMP homeostasis. This regulation is crucial for visual processing and photoreceptor viability. GCAP1 contains multiple EF-hand domains for Ca²⁺/Mg²⁺ binding and is myristoylated at its N-terminus. Pathogenic mutations in GUCA1A can disrupt the calcium-sensing or regulatory function, resulting in inherited forms of retinal degeneration, especially various cone and cone-rod dystrophies, due to altered cGMP and Ca²⁺ homeostasis in photoreceptors[1][2][3][4][5].

Other names

GUCA1AC6orf131GCAPGUCA1COD3dJ139D8.6CORD14GCAP-IGCAP-1Guanylate cyclase activator 1Acone dystrophy 3photoreceptor 1guanylin 1guanylyl cyclase-activating protein 1guanylate cyclase-activating protein, retina

Allosteric modulation of retinal guanylate cyclase (RetGC) activity (activation at low Ca²⁺/Mg²⁺-bound, inhibition at high Ca²⁺) Mutant forms can constitutively activate RetGC leading to photoreceptor pathology