UCLA

Biogenesis of Lysosome-related Organelles Complex 1 (BLOC-1) is a multimeric protein complex composed of eight subunits and involved in the intracellular trafficking of integral membrane proteins from early endosomes to lysosomes and lysosome-related organelles. The overall goal of this dissertation was to characterize BLOC-1 in the mouse brain and in vitro. Previous behavioral and electrophysiological studies of BLOC-1-deficient mice had suggested that BLOC-1 has a physiological function in the brain. The BLOC-1-deficient mouse brain was analyzed at postnatal day (P)1 and the brains of BLOC-1-deficient mice displayed subtle cytoarchitectural abnormalities specific to the hippocampus. Previous in vitro studies have shown that BLOC-1-deficient neurons have abnormalities in the development of their neurites. The brains from wild-type and BLOC-1-deficient mice were analyzed at P60, using the Golgi method. BLOC-1-deficient neurons from some of the hippocampal neurons had defects in their dendritic arborization. Two of the BLOC-1 subunits, dysbindin and pallidin, have alternatively spliced variants that are expressed in brain. In addition to these subunit variants, the genomes of humans and other mammals contain an uncharacterized gene encoding a paralog of the cappuccino subunit. Some of the alternative subunits were found to replace the full-length form and form a stable complex with the other BLOC-1 subunits. BLOC-1 is well described to have a physical interaction with another multimeric protein complex, Adaptor Protein (AP)-3. The minimal region within dysbindin to bind AP-3 was delineated and critical residues were identified.