The Hermansky-Pudlak syndrome (HPS) protein is part of a high molecular weight complex involved in biogenesis of early melanosomes

Oh, Jangsuk; Liu, Zhenxiang; Feng, Guo; Raposo, GraÃ§a; Spritz, Richard A.

doi:10.1093/hmg/9.3.375

Cited by 60 publications

(54 citation statements)

References 37 publications

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“…Third, BLOC-3 could play a rather indirect role, for instance by mediating the intracellular trafficking to late endosomes and lysosomes of a protein that, in turn, would be required for organelle attachment to microtubules and/or detachment from actin filaments. This third scenario, and not the first two, would be compatible with the intracellular localization reported for the HPS1 subunit of BLOC-3, which by immunogold labeling was found to be associated with tubulovesicular membrane profiles in the vicinity of the Golgi complex of lymphoblastoid cells (Oh et al, 2000). It is worth mentioning that a similar mechanism has been invoked to explain the defective movement of lytic granules, the lysosome-related organelles of cytotoxic T cells, in patients suffering from HPS-2 resulting from mutations in the gene encoding the ␤3A subunit of AP-3, a protein complex directly involved in protein trafficking (Clark et al, 2003).…”

Section: Discussionsupporting

confidence: 87%

Distribution and dynamics of Lamp1-containing endocytic organelles in fibroblasts deficient in BLOC-3

Falcón‐Pérez

Nazarian

Sabatti

et al. 2005

Journal of Cell Science

186

148

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Late endosomes and lysosomes of mammalian cells in interphase tend to concentrate in the perinuclear region that harbors the microtubule-organizing center. We have previously reported abnormal distribution of these organelles – as judged by reduced percentages of cells displaying pronounced perinuclear accumulation – in mutant fibroblasts lacking BLOC-3 (for `biogenesis of lysosome-related organelles complex 3'). BLOC-3 is a protein complex that contains the products of the genes mutated in Hermansky-Pudlak syndrome types 1 and 4. Here, we developed a method based on image analysis to estimate the extent of organelle clustering in the perinuclear region of cultured cells. Using this method, we corroborated that the perinuclear clustering of late endocytic organelles containing Lamp1 (for `lysosome-associated membrane protein 1') is reduced in BLOC-3-deficient murine fibroblasts, and found that it is apparently normal in fibroblasts deficient in BLOC-1 or BLOC-2, which are another two protein complexes associated with Hermansky-Pudlak syndrome. Wild-type and mutant fibroblasts were transfected to express human LAMP1 fused at its cytoplasmic tail to green fluorescence protein (GFP). At low expression levels, LAMP1-GFP was targeted correctly to late endocytic organelles in both wild-type and mutant cells. High levels of LAMP1-GFP overexpression elicited aberrant aggregation of late endocytic organelles, a phenomenon that probably involved formation of anti-parallel dimers of LAMP1-GFP as it was not observed in cells expressing comparable levels of a non-dimerizing mutant variant, LAMP1-mGFP. To test whether BLOC-3 plays a role in the movement of late endocytic organelles, time-lapse fluorescence microscopy experiments were performed using live cells expressing low levels of LAMP1-GFP or LAMP1-mGFP. Although active movement of late endocytic organelles was observed in both wild-type and mutant fibroblasts, quantitative analyses revealed a relatively lower frequency of microtubule-dependent movement events, either towards or away from the perinuclear region, within BLOC-3-deficient cells. By contrast, neither the duration nor the speed of these microtubule-dependent events seemed to be affected by the lack of BLOC-3 function. These results suggest that BLOC-3 function is required, directly or indirectly, for optimal attachment of late endocytic organelles to microtubule-dependent motors.

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Section: Discussionsupporting

confidence: 87%

Distribution and dynamics of Lamp1-containing endocytic organelles in fibroblasts deficient in BLOC-3

Falcón‐Pérez

Nazarian

Sabatti

et al. 2005

Journal of Cell Science

186

148

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“…In any event, the fact that the frictional ratio of BLOC-3 was larger than that expected for a spherical molecule (f/f 0 = 1) was consistent with a previous analysis of epitope-tagged forms of the complex [52] and provided a satisfactory explanation for why the molecular mass values calculated by a combination of size-exclusion chromatography and sedimentation velocity analysis (this work and Ref. [52]) were lower than those estimated using only the first method [15,53]. A native molecular mass of 140 ± 30 kDa for BLOC-3 is, consequently, most consistent with the idea that the complex exists as a HPS1•HPS4 heterodimer, although still the putative existence of a relatively small (<15 kDa) third subunit cannot be excluded at this point.…”

Section: Does Human Bloc-3 Contain Additional Subunits?supporting

confidence: 89%

“…2) could imply that these patients may bear mutations within the promoter, enhancer or intronic regions of these two genes or, alternatively, that they might carry mutations in a different gene encoding a putative third subunit of BLOC-3. The second alternative was considered given previous estimates of the native molecular mass of the complex, which ranged from ∼175 kDa [52] to ∼200 kDa [15,53] in non-pigmented cells and from ∼200 to over 500 kDa in melanin-producing melanoma cells [15,53]. Because the calculated molecular mass of a HPS1•HPS4 heterodimer approximates 156 kDa, the existence of one ore more additional BLOC-3 subunits was plausible.…”

Section: Does Human Bloc-3 Contain Additional Subunits?mentioning

confidence: 99%

An immunoblotting assay to facilitate the molecular diagnosis of Hermansky–Pudlak syndrome

Nazarian

Huizing

Helip-Wooley

et al. 2008

Molecular Genetics and Metabolism

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Hermansky-Pudlak syndrome (HPS) comprises a constellation of human autosomal recessive disorders characterized by albinism and platelet storage pool deficiency. At least eight types of HPS have been defined based on the identity of the mutated gene. These genes encode components of four ubiquitously expressed protein complexes, named Adaptor Protein (AP)-3 and Biogenesis of Lysosome-related Organelles Complex (BLOC)-1 through -3. In patients of Puerto Rican origin, the molecular diagnosis can be based on analysis of two founder mutations. On the other hand, identification of the HPS type in other patients relies on the sequencing of all candidate genes. In this work, we have developed a biochemical assay to minimize the number of candidate genes to be sequenced per patient. The assay consists of immunoblotting analysis of extracts prepared from skin fibroblasts, using antibodies to one subunit per protein complex. The assay allowed us to determine which complex was defective in each of a group of HPS patients with unknown genetic lesions, thus subsequent sequencing was limited to genes encoding the corresponding subunits. Because no mutations within the two genes encoding BLOC-3 subunits could be found in two patients displaying reduced BLOC-3 levels, the possible existence of additional subunits was considered. Through sizeexclusion chromatography and sedimentation velocity analysis, the native molecular mass of BLOC-3 was estimated to be 140 ± 30 kDa, a value most consistent with the idea that BLOC-3 is a HPS1•HPS4 heterodimer (∼156 kDa) albeit not inconsistent with the putative existence of a relatively small third subunit.

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“…7 The 79-kd HPS1 protein is largely cytosolic though a portion is weakly membrane-bound. 8,9 It is a component of a high-molecular-weight complex though its exact function in vesicle trafficking is unknown. The HPS1 and HPS4 proteins may function in the same pathway of organelle biogenesis.…”

Section: Introductionmentioning

confidence: 99%

The regulation of platelet-dense granules by Rab27a in the ashen mouse, a model of Hermansky-Pudlak and Griscelli syndromes, is granule-specific and dependent on genetic background

Novak

Gautam

Reddington

et al. 2002

Blood

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The ashen (ash) mouse, a model for Hermansky-Pudlak syndrome (HPS) and for a subset of patients with Griscelli syndrome, presents with hypopigmentation, prolonged bleeding times, and platelet storage pool deficiency due to a mutation which abrogates expression of the Rab27a protein. Platelets of mice with the ashen mutation on the C3H/HeSnJ inbred strain background have greatly reduced amounts of dense granule components such as serotonin and adenine nucleotides though near-normal numbers of dense granules as enumerated by the dense granule-specific fluorescent dye mepacrine. Thus, essentially normal numbers of platelet dense granules are produced but the granule interiors are abnormal. Collagen-mediated aggregation of mutant platelets is significantly depressed. No abnormalities in the concentrations or secretory rates of 2 other major platelet granules, lysosomes and alpha granules, were apparent. Similarly, no platelet ultrastructural alterations other than those involving dense granules were detected. Therefore, Rab27a regulates the synthesis and secretion of only one major platelet organelle, the dense granule. There were likewise no mutant effects on levels or secretion of lysosomal enzymes of several other tissues. Together with other recent analyses of the ashen mouse, these results suggest a close relationship between platelet dense granules, melanosomes of melanocytes and secretory lysosomes of cytotoxic T lymphocytes, all mediated by Rab27a. Surprisingly, the effects of the ashen mutation on plateletdense granule components, platelet aggregation, and bleeding times were highly dependent on genetic background. This suggests that bleeding tendencies may likewise vary among patients with Griscelli syndrome and HPS with Rab27a mutations. (Blood. 2002;100:128-135)

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The Hermansky-Pudlak syndrome (HPS) protein is part of a high molecular weight complex involved in biogenesis of early melanosomes

Cited by 60 publications

References 37 publications

Distribution and dynamics of Lamp1-containing endocytic organelles in fibroblasts deficient in BLOC-3

Distribution and dynamics of Lamp1-containing endocytic organelles in fibroblasts deficient in BLOC-3

An immunoblotting assay to facilitate the molecular diagnosis of Hermansky–Pudlak syndrome

The regulation of platelet-dense granules by Rab27a in the ashen mouse, a model of Hermansky-Pudlak and Griscelli syndromes, is granule-specific and dependent on genetic background

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