Introduction <table class="infobox infobox-protein">Gene </td>UniProt </td>Molecular Weight </td>Subcellular Localization </td>Protein Family </td>Aliases </td>
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Introduction <table class="infobox infobox-protein">Gene </td>UniProt </td>Molecular Weight </td>Subcellular Localization </td>Protein Family </td>Aliases </td>
RAB27A is a small GTPase belonging to the Rab family of proteins involved in vesicular trafficking. It plays a critical role in regulated secretion, particularly in neuroendocrine cells, immune cells, and melanocytes. Mutations in RAB27A cause Griscelli syndrome, a rare autosomal recessive disorder characterized by partial albinism, immunodeficiency, and neurological abnormalities.
:: infobox .infobox-protein
Structure
Protein Architecture RAB27A is a member of the Rab GTPase family with characteristic features:
GTP-binding domain : Five conserved motifs for nucleotide bindingSwitch I and II regions : Conformational changes upon GTP/GDP exchangeC-terminal CAAX motif : Cysteine methylation and prenylation for membrane anchoringHypervariable region : Determines effector specificityPost-Translational Modifications
Prenylation : C-terminal cysteine prenylation for membrane associationPalmitoylation : Additional lipid modificationGDP/GTP cycling : Active (GTP-bound) and inactive (GDP-bound) statesNormal Function
Vesicle Trafficking RAB27A regulates vesicle trafficking through:
Secretory granule exocytosis : Controls regulated secretion in neuroendocrine cellsLysosome-related organelle trafficking : Functions in melanosomes, lytic granulesSynaptic vesicle dynamics : Involved in neurotransmitter releaseAutophagosome-lysosome fusion : Role in autophagy
Effector Proteins RAB27A interacts with multiple effector proteins:
Slac2-a/MyRIP : Links RAB27A to actin filamentsMunc13-4 : Regulates dense-core vesicle exocytosisJFC1/Slp1 : Scaffold protein for exocytosisSynaptotagmin-like proteins : Calcium sensors for exocytosisCellular Distribution
Neuroendocrine cells (chromaffin cells, PC12 cells)
Immune cells (T cells, NK cells, mast cells)
Melanocytes
Neurons (synaptic terminals)
Platelets
Role in Disease
Griscelli Syndrome Type 2 (GS2) RAB27A mutations cause Griscelli syndrome type 2:
Clinical features :Partial albinism (silver-gray hair, pigmentary dilution)
Immunodeficiency (impaired T cell and NK cell function)
Hemophagocytic lymphohistiocytosis (HLH)
Neurologic abnormalities (in some patients)
Pathogenesis : Impaired secretory granule traffickingInheritance : Autosomal recessiveImmunodeficiency RAB27A is essential for immune cell function:
Cytotoxic T cells : Impaired granule releaseNK cells : Defective cytotoxicityMast cells : Altered degranulationPlatelets : Defective dense granule releaseNeurodegeneration Emerging evidence for RAB27A in neurodegeneration:
Alzheimer's disease : Altered Rab GTPase expressionParkinson's disease : Role in alpha-synuclein traffickingALS : Impaired vesicle transport in motor neuronsCancer RAB27A is overexpressed in several cancers:
Melanoma : Promotes metastasisPancreatic cancer : Associated with poor prognosisBreast cancer : Regulates exosome secretionTherapeutic Implications
Animal Models
Rab27a Knockout Mice
Display hypopigmentation
Show immunodeficiency
Impaired platelet function
Neurological deficits
Zebrafish Models
Morpholino knockdown recapitulates GS2 phenotype
Used for drug screening
Protein-Protein Interactions RAB27A interacts with:
GTP/GDP exchange factors (GEFs) : Activate RAB27AGTPase activating proteins (GAPs) : Inactivate RAB27AEffectors : Slac2-a, Munc13-4, JFC1Motor proteins : Myosin Va for transportSee Also
[RAB27A Gene](/genes/rab27a)
[Vesicular Trafficking in Neurodegeneration](/mechanisms/vesicular-trafficking)
[Griscelli Syndrome](/diseases/griscelli-syndrome)
[Synaptic Vesicle Proteins](/proteins/synaptic-vesicles)
[Rab GTPases](/proteins/rab-gtpases)
References
[Unknown, Fukuda M. RAB27A and its role in regulated secretion (2013) (2013)](https://doi.org/10.1016/j.yexcr.2013.03.006)
[Menasche G et al., RAB27A mutations cause Griscelli syndrome (2000) (2000)](https://doi.org/10.1016/S0140-6736(00)
[Haddad EK et al., RAB27A in immune cell function (2001) (2001)](https://doi.org/10.1084/jem.194.4.471)
[Barral DC et al., RAB27A in melanosome trafficking (2002) (2002)](https://doi.org/10.1016/S0092-8674(02)
[Zhang L et al., RAB27A in cancer metastasis (2018) (2018)](https://doi.org/10.1038/s41388-018-0392-z) Show full description