Hermansky-Pudlak syndrome protein complexes associate with phosphatidylinositol 4-kinase type II alpha in neuronal and non-neuronal cells.
The Hermansky-Pudlak syndrome is a disorder affecting endosome sorting. Disease is triggered by defects in any of 15 mouse gene products, which are part of five distinct cytosolic molecular complexes: AP-3, homotypic fusion and vacuole protein sorting, and BLOC-1, -2, and -3. To identify molecular associations of these complexes, we used in vivo cross-linking followed by purification of cross-linked AP-3 complexes and mass spectrometric identification of associated proteins. AP-3 was co-isolated with BLOC-1, BLOC-2, and homotypic fusion and vacuole protein sorting complex subunits; clathrin; and phosphatidylinositol-4-kinase type II alpha (PI4KIIalpha). We previously reported that this membrane-anchored enzyme is a regulator of AP-3 recruitment to membranes and a cargo of AP-3 ( Craige, B., Salazar, G., and Faundez, V. (2008) Mol. Biol. Cell 19, 1415-1426 ). Using cells deficient in different Hermansky-Pudlak syndrome complexes, we identified that BLOC-1, but not BLOC-2 or BLOC-3, deficiencies affect PI4KIIalpha inclusion into AP-3 complexes. BLOC-1, PI4KIIalpha, and AP-3 belong to a tripartite complex, and down-regulation of either PI4KIIalpha, BLOC-1, or AP-3 complexes led to similar LAMP1 phenotypes. Our analysis indicates that BLOC-1 complex modulates the association of PI4KIIalpha with AP-3. These results suggest that AP-3 and BLOC-1 act, either in concert or sequentially, to specify sorting of PI4KIIalpha along the endocytic route.
Salazar
Gloria
G
Department of Cell Biology and Medicine, Emory University, Atlanta, Georgia 30322, USA.
Zlatic
Stephanie
S
Craige
Branch
B
Peden
Andrew A
AA
Pohl
Jan
J
Faundez
Victor
V
D033963:Adaptor Protein Complex 3 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D004705:Endocytosis / Q000235:genetics; D011992:Endosomes / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D022861:Hermanski-Pudlak Syndrome / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*
D033963:Adaptor Protein Complex 3; C102160:HPS1 protein, human; C491131:Hps1 protein, mouse; D008565:Membrane Proteins; D046912:Multiprotein Complexes; C514871:PIP4K2A protein, human; D017853:Phosphotransferases (Alcohol Group Acceptor)