Affinage

BLOC1S5

Biogenesis of lysosome-related organelles complex 1 subunit 5 · UniProt Q8TDH9

Length
187 aa
Mass
21.6 kDa
Annotated
2026-06-09
34 papers in source corpus 9 papers cited in narrative 9 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

BLOC1S5 (Muted) is an obligate subunit of BLOC-1, a ~200 kDa cytosolic protein complex required for the biogenesis of lysosome-related organelles including melanosomes, platelet dense granules, and large dense-core vesicles (PMID:12019270, PMID:1912584). Within the complex it co-assembles with pallidin and cappuccino, and its loss reduces steady-state pallidin levels, establishing that Muted is needed both for complex assembly and for the stability of partner subunits (PMID:12019270, PMID:12576321). Functionally, BLOC-1/Muted drives selective cargo export during organelle maturation: in muted-deficient chromaffin cells, large dense-core vesicles are enlarged because chromogranin A fails to be exported from immature vesicles, impairing maturation, docking, and regulated secretion (PMID:25673877), and Muted is also required for the steady-state level and targeting of CD63 to these vesicles (PMID:27531610). The conserved role in lysosome-related organelle biogenesis is underscored by the Bombyx mori ortholog, whose disruption abolishes urate granule formation (PMID:28768207). Homozygous loss-of-function variants in human BLOC1S5 abolish BLOC-1 assembly and cause Hermansky-Pudlak syndrome type 11, with patient alleles failing to rescue pigmentation, complex assembly, or cargo trafficking in null melanocytes (PMID:32565547).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2002 High

    Established that Muted is a physical subunit of the BLOC-1 complex and a structural determinant of complex integrity, answering whether the muted gene product acts within a defined trafficking machine.

    Evidence Reciprocal Co-IP, immunodepletion, size-exclusion chromatography and sedimentation velocity in cell lines; loss of muted reduced pallidin levels

    PMID:12019270

    Open questions at the time
    • Stoichiometry and atomic-level subunit contacts not resolved
    • Direct binding interface with pallidin not mapped
  2. 2002 Medium

    Localized Muted to vesicles in melanocyte cell bodies and dendrites, linking the complex to vesicular trafficking compartments relevant to melanosome biogenesis.

    Evidence Transfection and subcellular localization imaging in melan-a melanocytes

    PMID:11912185

    Open questions at the time
    • Vesicle identity not molecularly defined
    • Endogenous (vs overexpressed) localization not confirmed
  3. 2003 Medium

    Showed cappuccino co-assembles with Muted and pallidin and that a frameshift mutation abolishes assembly, demonstrating that BLOC-1 integrity depends on intact inter-subunit interactions.

    Evidence Co-IP, genetic mapping and frameshift mutation analysis from an HPS mouse strain

    PMID:12576321

    Open questions at the time
    • Single lab
    • Direct Muted-cappuccino contact not isolated from the broader complex
  4. 2014 Medium

    Demonstrated gene-dosage-independent effects of Bloc1s5 loss on subunit and neuronal-marker transcripts, distinguishing its molecular phenotype from that of dysbindin.

    Evidence Mouse null alleles, qRT-PCR and western blot of brain BLOC-1 subunits and NMDA/GABAergic markers

    PMID:24713699

    Open questions at the time
    • Mechanism connecting BLOC-1 loss to neuronal transcript changes unresolved
    • Direct vs secondary effects not separated
  5. 2015 High

    Defined the cargo-level mechanism: Muted is required to export chromogranin A from immature large dense-core vesicles, linking complex function to organelle maturation and regulated secretion.

    Evidence Bloc1s5-null mouse chromaffin cells, EM, fractionation, knockdown and exocytosis assays

    PMID:25673877

    Open questions at the time
    • Molecular machinery of CgA export step not identified
    • Whether Muted directly recognizes cargo unknown
  6. 2016 Medium

    Extended the cargo role to CD63, showing Muted controls its steady-state level and targeting to large dense-core vesicles.

    Evidence Colocalization imaging, sucrose gradient fractionation in muted-deficient mouse adrenals

    PMID:27531610

    Open questions at the time
    • Direct vs indirect effect on CD63 stability unresolved
    • Single lab
  7. 2017 Medium

    Confirmed evolutionary conservation of the BLOC-1 subunit function in lysosome-related organelle biogenesis using an invertebrate ortholog.

    Evidence Positional cloning, RNA-seq, transposon insertion and siRNA knockdown in Bombyx mori (urate granule phenotype)

    PMID:28768207

    Open questions at the time
    • Conservation of complex composition in insects not biochemically defined
  8. 2020 High

    Established human disease causation, showing biallelic BLOC1S5 loss abolishes BLOC-1 assembly and causes Hermansky-Pudlak syndrome type 11.

    Evidence Patient platelet functional tests, Co-IP for complex assembly, complementation rescue with WT vs patient allele in Bloc1s5-/- melanocytes

    PMID:32565547

    Open questions at the time
    • Full clinical spectrum across patients not defined
    • Tissue-specific severity determinants unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • How BLOC-1/Muted physically selects and routes specific cargoes (CgA, CD63) during organelle maturation remains undefined.
  • No structure of BLOC-1 with Muted
  • Direct cargo-binding activity not demonstrated
  • Recruitment to specific vesicle subdomains unmapped

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 2
Localization
GO:0031410 cytoplasmic vesicle 3 GO:0005829 cytosol 1
Pathway
R-HSA-1852241 Organelle biogenesis and maintenance 3 R-HSA-5653656 Vesicle-mediated transport 2
Partners
BLOC1S6BLOC1S8
Complex memberships
BLOC-1

Evidence

Reading pass · 9 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2002 BLOC1S5 (Muted protein) is a subunit of BLOC-1 (biogenesis of lysosome-related organelles complex 1), a ~200 kDa asymmetric protein complex also containing pallidin. Co-immunoprecipitation and immunodepletion with anti-muted antibody confirmed muted as a BLOC-1 subunit. Loss of muted reduces steady-state pallidin protein levels, indicating muted is required for pallidin stability within the complex. Co-immunoprecipitation, immunodepletion, size-exclusion chromatography, sedimentation velocity analysis, subcellular fractionation The Journal of biological chemistry High 12019270
2002 The muted protein localizes within vesicles in both the cell body and dendrites of transfected melan-a melanocytes, consistent with a role in vesicle trafficking for biogenesis of melanosomes and lysosome-related organelles. Transfection and subcellular localization imaging in melan-a melanocytes Human molecular genetics Medium 11912185
2003 Cappuccino (CNO), a novel protein mutated in another HPS mouse strain, co-assembles with pallidin and muted within the BLOC-1 complex; a frameshift mutation in CNO abolishes its ability to interact in BLOC-1, demonstrating that BLOC-1 integrity requires intact subunit interactions. Co-immunoprecipitation, genetic mapping, mutation analysis Blood Medium 12576321
2015 In muted-deficient (Bloc1s5 null) adrenal chromaffin cells, large dense-core vesicles (LDCVs) are enlarged and chromogranin A (CgA) accumulates due to failure to export CgA from immature LDCVs, impairing LDCV maturation and docking. The size of the readily releasable pool and vesicle release frequency are reduced, indicating BLOC-1/muted is required for selective cargo export during LDCV biogenesis. Muted-deficient mouse model (mu/mu), electron microscopy, biochemical fractionation, muted knockdown in cell culture, exocytosis assays Journal of cell science High 25673877
2016 The muted protein is required for the steady-state level and targeting of CD63 to large dense-core vesicles (LDCVs) in chromaffin cells. In muted-deficient adrenal glands, CD63 levels are significantly decreased. CD63-YFP colocalizes with NPY-dsRed-labeled LDCVs and is enriched in LDCV fractions by sucrose density gradient fractionation. Colocalization imaging, sucrose density gradient fractionation, muted-deficient mouse model Yi chuan = Hereditas Medium 27531610
2014 Loss-of-function mutations in Bloc1s5 (muted, mu/mu) and Bloc1s8 (dysbindin, sdy/sdy) differentially affect BLOC-1 subunit transcript and protein levels, as well as NMDA receptor subunit transcripts and GABAergic interneuron markers in brain. Unlike dysbindin null, elimination of one or two copies of Bloc1s5 generates indistinguishable pallidin transcript phenotypes, demonstrating gene-dosage-independent effects on complex subunit expression. Mouse null allele genetics, qRT-PCR, western blot, brain transcript and protein analysis The Journal of biological chemistry Medium 24713699
2020 Homozygous loss-of-function variants in BLOC1S5 in human patients abolish BLOC-1 complex assembly (demonstrated by functional platelet testing showing absence of obligate BLOC-1 complex). Expression of a patient-derived BLOC1S5 deletion in Bloc1s5-/- melan-mu melanocytes failed to rescue pigmentation, BLOC-1 complex assembly, or melanosome cargo trafficking, whereas wild-type BLOC1S5 restored these functions. Patient platelet functional tests, co-immunoprecipitation for BLOC-1 assembly, complementation assay in Bloc1s5-/- melanocytes (rescue of pigmentation and cargo trafficking) Genetics in medicine : official journal of the American College of Medical Genetics High 32565547
1991 The muted mouse mutation causes platelet storage pool deficiency characterized by abnormal dense granules, prolonged bleeding time, minimal ATP secretion upon collagen stimulation, and partially reduced lysosomal enzyme secretion from kidney proximal tubule cells, establishing that the muted gene simultaneously controls melanosomes, platelet dense granules, and lysosomes. Whole mount electron microscopy of platelets, mepacrine labeling, platelet aggregation/ATP secretion assay, lysosomal enzyme secretion assay Blood Medium 1912584
2017 Bm-muted, the Bombyx mori ortholog of mouse Muted/BLOC1S5, encodes a BLOC-1 subunit 5; its disruption by transposon insertion causes loss of urate granule formation in epidermal cells, resulting in translucent larval skin. siRNA-mediated knockdown confirmed the phenotype, establishing the conserved role of this BLOC-1 subunit in lysosome-related organelle biogenesis. Positional cloning, RNA-seq, siRNA knockdown, transposon insertion analysis Gene Medium 28768207

Source papers

Stage 0 corpus · 34 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2002 BLOC-1, a novel complex containing the pallidin and muted proteins involved in the biogenesis of melanosomes and platelet-dense granules. The Journal of biological chemistry 153 12019270
2017 KEAP1-modifying small molecule reveals muted NRF2 signaling responses in neural stem cells from Huntington's disease patients. Proceedings of the National Academy of Sciences of the United States of America 110 28533375
2015 The muted sense: neurocognitive limitations of olfactory language. Trends in cognitive sciences 108 25979848
2003 Cappuccino, a mouse model of Hermansky-Pudlak syndrome, encodes a novel protein that is part of the pallidin-muted complex (BLOC-1). Blood 76 12576321
2009 Interferon-alpha mediates suppression of C-reactive protein: explanation for muted C-reactive protein response in lupus flares? Arthritis and rheumatism 69 19950271
2002 The gene for the muted (mu) mouse, a model for Hermansky-Pudlak syndrome, defines a novel protein which regulates vesicle trafficking. Human molecular genetics 65 11912185
2020 BLOC1S5 pathogenic variants cause a new type of Hermansky-Pudlak syndrome. Genetics in medicine : official journal of the American College of Medical Genetics 62 32565547
1991 Platelet storage pool deficiency associated with inherited abnormalities of the inner ear in the mouse pigment mutants muted and mocha. Blood 58 1912584
1981 Vesicular stomatitis virus defective interfering particle containing a muted internal leader RNA gene. Proceedings of the National Academy of Sciences of the United States of America 36 6264463
2014 Mutations in the BLOC-1 subunits dysbindin and muted generate divergent and dosage-dependent phenotypes. The Journal of biological chemistry 30 24713699
2012 Individuals with increased inflammatory response to ozone demonstrate muted signaling of immune cell trafficking pathways. Respiratory research 26 23033980
2010 Activation of ataxia telangiectasia muted under experimental models and human Parkinson's disease. Cellular and molecular life sciences : CMLS 26 20502937
2022 Staphylococcus aureus induces a muted host response in human blood that blunts the recruitment of neutrophils. Proceedings of the National Academy of Sciences of the United States of America 21 35881802
2017 Bm-muted, orthologous to mouse muted and encoding a subunit of the BLOC-1 complex, is responsible for the otm translucent mutation of the silkworm Bombyx mori. Gene 20 28768207
2023 An Fc-muted bispecific antibody targeting PD-L1 and 4-1BB induces antitumor immune activity in colorectal cancer without systemic toxicity. Cellular & molecular biology letters 18 37259060
2016 Preservation of epithelial cell barrier function and muted inflammation in resistance to allergic rhinoconjunctivitis from house dust mite challenge. The Journal of allergy and clinical immunology 16 27658763
2017 Deletion of the K1L Gene Results in a Vaccinia Virus That Is Less Pathogenic Due to Muted Innate Immune Responses, yet Still Elicits Protective Immunity. Journal of virology 15 28490586
1995 Molecular markers near two mouse chromosome 13 genes, muted and pearl, which cause platelet storage pool deficiency (SPD). Mammalian genome : official journal of the International Mammalian Genome Society 13 7719021
2023 Marburg and Ebola Virus Infections Elicit a Complex, Muted Inflammatory State in Bats. Viruses 12 36851566
2021 Hepatic Steatosis in the Mouse Model of Wilson Disease Coincides with a Muted Inflammatory Response. The American journal of pathology 12 34627751
2015 Impaired maturation of large dense-core vesicles in muted-deficient adrenal chromaffin cells. Journal of cell science 12 25673877
2021 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 11 34685610
2024 Lost in translation? Evidence for a muted proteomic response to thermal stress in a stenothermal Antarctic fish and possible evolutionary mechanisms. Physiological genomics 5 39250150
2020 Single-wavelength water muted photoacoustic system for detecting physiological concentrations of endogenous molecules. Biomedical optics express 5 33659094
2014 Uncovering the multifaceted-self in the domain of negative traits: on the muted expression of negative self-knowledge. Personality & social psychology bulletin 4 24398541
2013 Proposal for generating new beta cells in a muted immune environment for type 1 diabetes. Diabetes/metabolism research and reviews 4 23853103
1995 Low ICAM-1 expression in the epidermis of depigmenting C57BL/6J-mivit/mivit mice: a possible cause of muted contact sensitization. Experimental dermatology 4 7757328
2024 An enhanced IL17 and muted type I interferon nasal epithelial cell state characterizes severe COVID-19 with fungal coinfection. Microbiology spectrum 2 38687064
2022 US Severe Acute Respiratory Syndrome Coronavirus 2 Epsilon Variant: Highly Transmissible but With an Adjusted Muted Host T-Cell Response. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 2 35438777
2018 Fortune and hindsight: gene patents' muted effect on medical practice. British medical bulletin 2 29608656
2026 DNA electroporation of HIV Env elicits robust T cell responses and memory B cell responses with muted serum antibody levels that can be boosted with recombinant protein. Vaccine 0 41865485
2025 Female Anterior Cruciate Ligaments Exhibit a Muted Mechanobiological Response to Mechanical Loading. bioRxiv : the preprint server for biology 0 41030974
2025 Female Anterior Cruciate Ligaments Exhibit a Muted Mechanobiological Response to Mechanical Loading. Journal of orthopaedic research : official publication of the Orthopaedic Research Society 0 41094729
2016 Muted protein is involved in the targeting of CD63 to large dense-core vesicles of chromaffin cells. Yi chuan = Hereditas 0 27531610

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