| Primary Identifier | IPR017218 | Type | Family |
| Short Name | BLOC-2_complex_Hps6_subunit |
| description | Lysosome-related organelles comprise a group of specialised intracellular compartments that include melanosomes and platelet dense granules in mammals and eye pigment granules in insects. Hermansky-Pudlak syndrome (HPS) is a disorder of lysosome-related organelle biogenesis. Genes associated with HPS encode subunits of three complexes that are known as biogenesis of lysosome-related organelles complex (BLOC)-1, -2 and -3 []. There are eight known HPS proteins of the BLOCs [, ]]. Organelles affected in HPS include the melanosome, resulting in hypopigmentation, and the platelet delta (dense) granule, resulting in prolonged bleeding times. HPS in humans or mice is caused by mutations in any of 15 genes, five of which encode subunits BLOC-1. BLOC-1 and BLOC-2 act sequentially in the same pathway. Melanosome maturation requires at least two cargo transport pathways directly from early endosomes to melanosomes. One pathway mediated by AP-3, and one pathway mediated by BLOC-1 and BLOC-2 []. The adaptor protein AP-3 complex is a component of the cellular machinery that controls protein sorting from endosomes to lysosomes and melanosomes. BLOC-1 interacts physically and functionally with AP-3 to facilitate the trafficking of a known AP-3 cargo, CD63, and of tyrosinase-related protein 1 (Tyrp1). BLOC-1 also interacts with BLOC-2 to facilitate Tyrp1 trafficking by a mechanism apparently independent of AP-3 function. Both BLOC-1 and -2 predominantly localise to early endosome-associated tubules [].Complex-2 (BLOC-2) contains the HPS3, HPS5 and HPS6 proteins as subunits. Fibroblasts deficient in the BLOC-2 subunits HPS3 or HPS6 have normal basal secretion function of the lysosomal enzyme beta-hexosaminidase [].This entry includes BLOC-2 complex, Hps6 subunit, which may regulate the synthesis and function of lysosomes and of highly specialized organelles []. It acts as cargo adapter for the dynein-dynactin motor complex to mediate the transport of lysosomes from the cell periphery to the perinuclear region. Hsp6 facilitates retrograde lysosomal trafficking by linking the motor complex to lysosomes, and perinuclear positioning of lysosomes is crucial for the delivery of endocytic cargos to lysosomes, for lysosome maturation and function []. |
