scholarly journals BLOC-1 Is Required for Cargo-specific Sorting from Vacuolar Early Endosomes toward Lysosome-related Organelles

2007 ◽  
Vol 18 (3) ◽  
pp. 768-780 ◽  
Author(s):  
Subba Rao Gangi Setty ◽  
Danièle Tenza ◽  
Steven T. Truschel ◽  
Evelyn Chou ◽  
Elena V. Sviderskaya ◽  
...  
Keyword(s):  
Protein Complex ◽  
Genetic Disorder ◽  
Adaptor Protein ◽  
Transport Pathways ◽  
Cargo Transport ◽  
Early Endosomes ◽  
Hermansky Pudlak Syndrome ◽  
Lysosome Related Organelles ◽  
And Function ◽  
Tyrosinase Related Protein

Hermansky-Pudlak syndrome (HPS) is a genetic disorder characterized by defects in the formation and function of lysosome-related organelles such as melanosomes. HPS in humans or mice is caused by mutations in any of 15 genes, five of which encode subunits of biogenesis of lysosome-related organelles complex (BLOC)-1, a protein complex with no known function. Here, we show that BLOC-1 functions in selective cargo exit from early endosomes toward melanosomes. BLOC-1–deficient melanocytes accumulate the melanosomal protein tyrosinase-related protein-1 (Tyrp1), but not other melanosomal proteins, in endosomal vacuoles and the cell surface due to failed biosynthetic transit from early endosomes to melanosomes and consequent increased endocytic flux. The defects are corrected by restoration of the missing BLOC-1 subunit. Melanocytes from HPS model mice lacking a different protein complex, BLOC-2, accumulate Tyrp1 in distinct downstream endosomal intermediates, suggesting that BLOC-1 and BLOC-2 act sequentially in the same pathway. By contrast, intracellular Tyrp1 is correctly targeted to melanosomes in melanocytes lacking another HPS-associated protein complex, adaptor protein (AP)-3. The results indicate that 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, that are deficient in several forms of HPS.

scholarly journals BLOC-1 Interacts with BLOC-2 and the AP-3 Complex to Facilitate Protein Trafficking on Endosomes

2006 ◽  
Vol 17 (9) ◽  
pp. 4027-4038 ◽  
Author(s):  
Santiago M. Di Pietro ◽  
Juan M. Falcón-Pérez ◽  
Danièle Tenza ◽  
Subba R.G. Setty ◽  
Michael S. Marks ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Protein Trafficking ◽  
Adaptor Protein ◽  
Early Endosome ◽  
Related Protein ◽  
Genes Encoding ◽  
Cellular Machinery ◽  
Hermansky Pudlak Syndrome ◽  
Lysosome Related Organelles ◽  
Tyrosinase Related Protein

The adaptor protein (AP)-3 complex is a component of the cellular machinery that controls protein sorting from endosomes to lysosomes and specialized related organelles such as melanosomes. Mutations in an AP-3 subunit underlie a form of Hermansky-Pudlak syndrome (HPS), a disorder characterized by abnormalities in lysosome-related organelles. HPS in humans can also be caused by mutations in genes encoding subunits of three complexes of unclear function, named biogenesis of lysosome-related organelles complex (BLOC)-1, -2, and -3. Here, we report that 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), a melanosomal membrane protein previously thought to traffic only independently of AP-3. 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 localize mainly to early endosome-associated tubules as determined by immunoelectron microscopy. These findings support the idea that BLOC-1 and -2 represent hitherto unknown components of the endosomal protein trafficking machinery.

scholarly journals Sorting to Synaptic-like Microvesicles from Early and Late Endosomes Requires Overlapping but Not Identical Targeting Signals

2000 ◽  
Vol 11 (5) ◽  
pp. 1801-1814 ◽  
Author(s):  
Anastasiya D. Blagoveshchenskaya ◽  
Daniel F. Cutler
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Pc12 Cells ◽  
Protein Complex ◽  
Adaptor Protein ◽  
Neuroendocrine Cells ◽  
Dependent Manner ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Epidermal Growth

In PC12 neuroendocrine cells, synaptic-like microvesicles (SLMV) are thought to be formed by two pathways. One pathway sorts the proteins to SLMV directly from the plasma membrane (or a specialized domain thereof) in an adaptor protein complex 2-dependent, brefeldin A (BFA)-insensitive manner. Another pathway operates via an endosomal intermediate, involves adaptor protein complex 3, and is BFA sensitive. We have previously shown that when expressed in PC12 cells, HRP-P-selectin chimeras are directed to SLMV mostly via the endosomal, BFA-sensitive route. We have now found that two endosomal intermediates are involved in targeting of HRP-P-selectin chimeras to SLMV. The first intermediate is the early, transferrin-positive, epidermal growth factor-positive endosome, from which exit to SLMV is controlled by the targeting determinants YGVF and KCPL, located within the cytoplasmic domain of P-selectin. The second intermediate is the late, transferrin-negative, epidermal growth factor-positive late endosome, from where HRP-P-selectin chimeras are sorted to SLMV in a YGVF- and DPSP-dependent manner. Both sorting steps, early endosomes to SLMV and late endosomes to SLMV, are affected by BFA. In addition, analysis of double mutants with alanine substitutions of KCPL and YGVF or KCPL and DPSP indicated that chimeras pass sequentially through these intermediates en route both to lysosomes and to SLMV. We conclude that a third site of formation for SLMV, the late endosomes, exists in PC12 cells.

scholarly journals The WASH complex, an endosomal Arp2/3 activator, interacts with the Hermansky–Pudlak syndrome complex BLOC-1 and its cargo phosphatidylinositol-4-kinase type IIα

2013 ◽  
Vol 24 (14) ◽  
pp. 2269-2284 ◽  
Author(s):  
P. V. Ryder ◽  
R. Vistein ◽  
A. Gokhale ◽  
M. N. Seaman ◽  
M. A. Puthenveedu ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Adaptor Protein ◽  
Coat Proteins ◽  
Lipid Kinase ◽  
Rho Family Gtpases ◽  
Vesicle Biogenesis ◽  
Hermansky Pudlak Syndrome ◽  
Rho Family ◽  
Lysosome Related Organelles ◽  
Phosphatidylinositol 4

Vesicle biogenesis machinery components such as coat proteins can interact with the actin cytoskeleton for cargo sorting into multiple pathways. It is unknown, however, whether these interactions are a general requirement for the diverse endosome traffic routes. In this study, we identify actin cytoskeleton regulators as previously unrecognized interactors of complexes associated with the Hermansky–Pudlak syndrome. Two complexes mutated in the Hermansky–Pudlak syndrome, adaptor protein complex-3 and biogenesis of lysosome-related organelles complex-1 (BLOC-1), interact with and are regulated by the lipid kinase phosphatidylinositol-4-kinase type IIα (PI4KIIα). We therefore hypothesized that PI4KIIα interacts with novel regulators of these complexes. To test this hypothesis, we immunoaffinity purified PI4KIIα from isotope-labeled cell lysates to quantitatively identify interactors. Strikingly, PI4KIIα isolation preferentially coenriched proteins that regulate the actin cytoskeleton, including guanine exchange factors for Rho family GTPases such as RhoGEF1 and several subunits of the WASH complex. We biochemically confirmed several of these PI4KIIα interactions. Of importance, BLOC-1 complex, WASH complex, RhoGEF1, or PI4KIIα depletions altered the content and/or subcellular distribution of the BLOC-1–sensitive cargoes PI4KIIα, ATP7A, and VAMP7. We conclude that the Hermansky–Pudlak syndrome complex BLOC-1 and its cargo PI4KIIα interact with regulators of the actin cytoskeleton.

scholarly journals Rag GTPases and phosphatidylinositol 3-phosphate mediate recruitment of the AP-5/SPG11/SPG15 complex

2021 ◽  
Vol 220 (2) ◽  
Author(s):  
Jennifer Hirst ◽  
Geoffrey G. Hesketh ◽  
Anne-Claude Gingras ◽  
Margaret S. Robinson
Keyword(s):  
Protein Complex ◽  
Adaptor Protein ◽  
Coincidence Detection ◽  
Rag Gtpases ◽  
Fyve Domain ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Mtorc1 Pathway ◽  
Phosphatidylinositol 3

Adaptor protein complex 5 (AP-5) and its partners, SPG11 and SPG15, are recruited onto late endosomes and lysosomes. Here we show that recruitment of AP-5/SPG11/SPG15 is enhanced in starved cells and occurs by coincidence detection, requiring both phosphatidylinositol 3-phosphate (PI3P) and Rag GTPases. PI3P binding is via the SPG15 FYVE domain, which, on its own, localizes to early endosomes. GDP-locked RagC promotes recruitment of AP-5/SPG11/SPG15, while GTP-locked RagA prevents its recruitment. Our results uncover an interplay between AP-5/SPG11/SPG15 and the mTORC1 pathway and help to explain the phenotype of AP-5/SPG11/SPG15 deficiency in patients, including the defect in autophagic lysosome reformation.

scholarly journals A Novel Likely Pathogenic Variant in the BLOC1S5 Gene Associated with Hermansky-Pudlak Syndrome Type 11 and an Overview of Human BLOC-1 Deficiencies

Cells ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2630
Author(s):  
Doris Boeckelmann ◽  
Mira Wolter ◽  
Barbara Käsmann-Kellner ◽  
Udo Koehler ◽  
Lea Schieber-Nakamura ◽  
...  
Keyword(s):  
Genetic Defect ◽  
Adaptor Protein ◽  
Genetic Alterations ◽  
Oculocutaneous Albinism ◽  
Pathogenic Variants ◽  
New Type ◽  
Hermansky Pudlak Syndrome ◽  
Lysosome Related Organelles ◽  
Next Generation Sequencing Ngs ◽  
Generation Sequencing

Hermansky-Pudlak syndrome (HPS) is a heterogeneous disorder combining oculocutaneous albinism (OCA) and a platelet function disorder of varying severity as its most prominent features. The genes associated with HPS encode for different BLOC- (biogenesis of lysosome-related organelles complex) complexes and for the AP-3 (adaptor protein-3) complex, respectively. These proteins are involved in maturation, trafficking, and the function of lysosome-related organelles (LROs) such as melanosomes and platelet δ-granules. Some patients with different types of HPS can develop additional complications and symptoms like pulmonary fibrosis, granulomatous colitis, and immunodeficiency. A new type of HPS has recently been identified associated with genetic alterations in the BLOC1S5 gene, which encodes the subunit Muted of the BLOC-1 complex. Our aim was to unravel the genetic defect in two siblings with a suspected HPS diagnosis (because of OCA and bleeding symptoms) using next generation sequencing (NGS). Platelet functional analysis revealed reduced platelet aggregation after stimulation with ADP and a severe secretion defect in platelet δ-granules. NGS identified a novel homozygous essential splice site variant in the BLOC1S5 gene present in both affected siblings who are descendants of a consanguine marriage. The patients exhibited no additional symptoms. Our study confirms that pathogenic variants of BLOC1S5 cause the recently described HPS type 11.

scholarly journals SLC35D3 delivery from megakaryocyte early endosomes is required for platelet dense granule biogenesis and is differentially defective in Hermansky-Pudlak syndrome models

Blood ◽  
2012 ◽  
Vol 120 (2) ◽  
pp. 404-414 ◽  
Author(s):  
Ronghua Meng ◽  
Yuhuan Wang ◽  
Yu Yao ◽  
Zhe Zhang ◽  
Dawn C. Harper ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Subcellular Fractionation ◽  
Dense Granule ◽  
Direct Role ◽  
Excessive Bleeding ◽  
Dense Granules ◽  
Early Endosomes ◽  
Hermansky Pudlak Syndrome ◽  
Endosomal Transport ◽  
Lysosome Related Organelles

Abstract Platelet dense granules are members of a family of tissue-specific, lysosome-related organelles that also includes melanosomes in melanocytes. Contents released from dense granules after platelet activation promote coagulation and hemostasis, and dense granule defects such as those seen in Hermansky-Pudlak syndrome (HPS) cause excessive bleeding, but little is known about how dense granules form in megakaryocytes (MKs). In the present study, we used SLC35D3, mutation of which causes a dense granule defect in mice, to show that early endosomes play a direct role in dense granule biogenesis. We show that SLC35D3 expression is up-regulated during mouse MK differentiation and is enriched in platelets. Using immunofluorescence and immunoelectron microscopy and subcellular fractionation in megakaryocytoid cells, we show that epitope-tagged and endogenous SLC35D3 localize predominantly to early endosomes but not to dense granule precursors. Nevertheless, SLC35D3 is depleted in mouse platelets from 2 of 3 HPS models and, when expressed ectopically in melanocytes, SLC35D3 localizes to melanosomes in a manner requiring a HPS-associated protein complex that functions from early endosomal transport intermediates. We conclude that SLC35D3 is either delivered to nascent dense granules from contiguous early endosomes as MKs mature or functions in dense granule biogenesis directly from early endosomes, suggesting that dense granules originate from early endosomes in MKs.

Hermansky-Pudlak syndrome

2014 ◽  
Vol 34 (04) ◽  
pp. 301-309 ◽  
Author(s):  
I. Sánchez-Guiu ◽  
J. M. Torregrosa ◽  
F. Velasco ◽  
A. I. Antón ◽  
M. L. Lozano ◽  
...  
Keyword(s):  
Molecular Characterization ◽  
Clinical Management ◽  
Autosomal Recessive Disorder ◽  
Molecular Heterogeneity ◽  
Platelet Function Test ◽  
Hermansky Pudlak Syndrome ◽  
Lysosome Related Organelles ◽  
And Function

SummaryHermansky-Pudlak syndrome (HPS) is a rare, autosomal recessive disorder affecting lysosome-related organelles (LRO), including dense platelet granules. HPS causes oculo- cutaneous hypopigmentation, bleeding diathesis and granulomatous colitis or pulmonary fibrosis. To date, there is no curative treatment and the clinical management depends on the severity of symptoms. A prompt diagnosis of HPS patients could improve their quality of life and clinical management. However, the absence of a specific platelet function test, the wide molecular heterogeneity, and the lack of phenotypegenotype correlations hamper the rapid diagnosis. Nine subtypes of HPS have been identified as a result of mutations in nine genes that codify for proteins involved in formation and shuttle of the LRO. The molecular characterization of patients and knowledge derived from animal models of HPS contribute to the understanding of biogenesis and function of the LRO.This paper describes a patient with a novel homozygous nonsense mutation causing HPS and provides a review of the literature focusing on recent advances in the molecular characterization and physiopathology of HPS.

scholarly journals BLOC-2 targets recycling endosomal tubules to melanosomes for cargo delivery

2015 ◽  
Vol 209 (4) ◽  
pp. 563-577 ◽  
Author(s):  
Megan K. Dennis ◽  
Adriana R. Mantegazza ◽  
Olivia L. Snir ◽  
Danièle Tenza ◽  
Amanda Acosta-Ruiz ◽  
...  
Keyword(s):  
Live Cell Imaging ◽  
Cell Imaging ◽  
Pigment Cell ◽  
Wild Type ◽  
Transport Pathway ◽  
Cargo Transport ◽  
Cargo Delivery ◽  
Tubular Transport ◽  
Hermansky Pudlak Syndrome ◽  
Lysosome Related Organelles

Hermansky–Pudlak syndrome (HPS) is a group of disorders characterized by the malformation of lysosome-related organelles, such as pigment cell melanosomes. Three of nine characterized HPS subtypes result from mutations in subunits of BLOC-2, a protein complex with no known molecular function. In this paper, we exploit melanocytes from mouse HPS models to place BLOC-2 within a cargo transport pathway from recycling endosomal domains to maturing melanosomes. In BLOC-2–deficient melanocytes, the melanosomal protein TYRP1 was largely depleted from pigment granules and underwent accelerated recycling from endosomes to the plasma membrane and to the Golgi. By live-cell imaging, recycling endosomal tubules of wild-type melanocytes made frequent and prolonged contacts with maturing melanosomes; in contrast, tubules from BLOC-2–deficient cells were shorter in length and made fewer, more transient contacts with melanosomes. These results support a model in which BLOC-2 functions to direct recycling endosomal tubular transport intermediates to maturing melanosomes and thereby promote cargo delivery and optimal pigmentation.

scholarly journals Roles of BLOC-1 and Adaptor Protein-3 Complexes in Cargo Sorting to Synaptic Vesicles

2009 ◽  
Vol 20 (5) ◽  
pp. 1441-1453 ◽  
Author(s):  
Karen Newell-Litwa ◽  
Gloria Salazar ◽  
Yoland Smith ◽  
Victor Faundez
Keyword(s):  
Membrane Proteins ◽  
Synaptic Vesicle ◽  
Synaptic Vesicles ◽  
Adaptor Protein ◽  
Protein Composition ◽  
Organelle Biogenesis ◽  
Vesicle Membrane ◽  
Early Endosomes ◽  
Lysosomal Sorting ◽  
Lysosome Related Organelles

Neuronal lysosomes and their biogenesis mechanisms are primarily thought to clear metabolites and proteins whose abnormal accumulation leads to neurodegenerative disease pathology. However, it remains unknown whether lysosomal sorting mechanisms regulate the levels of membrane proteins within synaptic vesicles. Using high-resolution deconvolution microscopy, we identified early endosomal compartments where both selected synaptic vesicle and lysosomal membrane proteins coexist with the adaptor protein complex 3 (AP-3) in neuronal cells. From these early endosomes, both synaptic vesicle membrane proteins and characteristic AP-3 lysosomal cargoes can be similarly sorted to brain synaptic vesicles and PC12 synaptic-like microvesicles. Mouse knockouts for two Hermansky–Pudlak complexes involved in lysosomal biogenesis from early endosomes, the ubiquitous isoform of AP-3 (Ap3b1−/−) and muted, defective in the biogenesis of lysosome-related organelles complex 1 (BLOC-1), increased the content of characteristic synaptic vesicle proteins and known AP-3 lysosomal proteins in isolated synaptic vesicle fractions. These phenotypes contrast with those of the mouse knockout for the neuronal AP-3 isoform involved in synaptic vesicle biogenesis (Ap3b2−/−), in which the content of select proteins was reduced in synaptic vesicles. Our results demonstrate that lysosomal and lysosome-related organelle biogenesis mechanisms regulate steady-state synaptic vesicle protein composition from shared early endosomes.

scholarly journals BLOC-1 and BLOC-3 regulate VAMP7 cycling to and from melanosomes via distinct tubular transport carriers

2016 ◽  
Vol 214 (3) ◽  
pp. 293-308 ◽  
Author(s):  
Megan K. Dennis ◽  
Cédric Delevoye ◽  
Amanda Acosta-Ruiz ◽  
Ilse Hurbain ◽  
Maryse Romao ◽  
...  
Keyword(s):  
Live Cell Imaging ◽  
Rab Gtpase ◽  
Cargo Delivery ◽  
Cargo Protein ◽  
Early Endosomes ◽  
Tubular Transport ◽  
Hermansky Pudlak Syndrome ◽  
Recycling Pathway ◽  
Lysosome Related Organelles ◽  
Dependent Transport

Endomembrane organelle maturation requires cargo delivery via fusion with membrane transport intermediates and recycling of fusion factors to their sites of origin. Melanosomes and other lysosome-related organelles obtain cargoes from early endosomes, but the fusion machinery involved and its recycling pathway are unknown. Here, we show that the v-SNARE VAMP7 mediates fusion of melanosomes with tubular transport carriers that also carry the cargo protein TYRP1 and that require BLOC-1 for their formation. Using live-cell imaging, we identify a pathway for VAMP7 recycling from melanosomes that employs distinct tubular carriers. The recycling carriers also harbor the VAMP7-binding scaffold protein VARP and the tissue-restricted Rab GTPase RAB38. Recycling carrier formation is dependent on the RAB38 exchange factor BLOC-3. Our data suggest that VAMP7 mediates fusion of BLOC-1–dependent transport carriers with melanosomes, illuminate SNARE recycling from melanosomes as a critical BLOC-3–dependent step, and likely explain the distinct hypopigmentation phenotypes associated with BLOC-1 and BLOC-3 deficiency in Hermansky–Pudlak syndrome variants.

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