Biogenesis of lysosomal organelles complex 3 subunit 2 (HPS4)

Biogenesis of lysosomal organelles complex 3 subunit 2 (HPS4) is a protein that forms a stable heterodimeric complex with HPS1, known as the BLOC-3 complex[1][2]. This complex is involved in the trafficking and biogenesis of lysosome-related organelles, including melanosomes in pigment cells and platelet dense granules. BLOC-3 acts as a guanine nucleotide exchange factor (GEF) for the small GTPases RAB32 and RAB38 and is an effector of RAB9A, thereby regulating essential processes in vesicle trafficking and organelle function[1]. Mutations in HPS4 disrupt this complex and lead to Hermansky-Pudlak syndrome type 4, a rare autosomal recessive disorder characterized by albinism, bleeding diathesis, and, in some subtypes, fatal pulmonary fibrosis[1][2]. HPS4 itself is not classically considered a direct therapeutic drug target such as a receptor or enzyme, but pathogenic variants in HPS4 are clinically relevant for diagnosis and disease understanding in the context of lysosome-related organelle diseases[2].

Other names

BLOC-3 complex member HPS4KIAA1667LE (light-ear protein homolog)BLOC3S2Hermansky-Pudlak syndrome 4 protein