Ras-related protein Rab-8B (RAB8B)

The protein contains 207 amino acids for an estimated molecular weight of 23584 Da.

 

The small GTPases Rab are key regulators of intracellular membrane trafficking, from the formation of transport vesicles to their fusion with membranes. Rabs cycle between an inactive GDP-bound form and an active GTP-bound form that is able to recruit to membranes different sets of downstream effectors directly responsible for vesicle formation, movement, tethering and fusion. That Rab may be involved in polarized vesicular trafficking and neurotransmitter release. May participate in cell junction dynamics in Sertoli cells (By similarity). (updated: April 1, 2015)

Protein identification was indicated in the following studies:

  1. Goodman and co-workers. (2013) The proteomics and interactomics of human erythrocytes. Exp Biol Med (Maywood) 238(5), 509-518.
  2. Lange and co-workers. (2014) Annotating N termini for the human proteome project: N termini and Nα-acetylation status differentiate stable cleaved protein species from degradation remnants in the human erythrocyte proteome. J Proteome Res. 13(4), 2028-2044.
  3. Hegedűs and co-workers. (2015) Inconsistencies in the red blood cell membrane proteome analysis: generation of a database for research and diagnostic applications. Database (Oxford) 1-8.
  4. Wilson and co-workers. (2016) Comparison of the Proteome of Adult and Cord Erythroid Cells, and Changes in the Proteome Following Reticulocyte Maturation. Mol Cell Proteomics. 15(6), 1938-1946.
  5. Bryk and co-workers. (2017) Quantitative Analysis of Human Red Blood Cell Proteome. J Proteome Res. 16(8), 2752-2761.
  6. D'Alessandro and co-workers. (2017) Red blood cell proteomics update: is there more to discover? Blood Transfus. 15(2), 182-187.
  7. Chu and co-workers. (2018) Quantitative mass spectrometry of human reticulocytes reveal proteome-wide modifications during maturation. Br J Haematol. 180(1), 118-133.

Methods

The following articles were analysed to gather the proteome content of erythrocytes.

The gene or protein list provided in the studies were processed using the ID mapping API of Uniprot in September 2018. The number of proteins identified and mapped without ambiguity in these studies is indicated below.
Only Swiss-Prot entries (reviewed) were considered for protein evidence assignation.

PublicationIdentification 1Uniprot mapping 2Not mapped /
Obsolete		TrEMBLSwiss-Prot
Goodman (2013)2289 (gene list)227853205992269
Lange (2014)123412347281224
Hegedus (2015)2638262202352387
Wilson (2016)165815281702911068
d'Alessandro (2017)18261817201815
Bryk (2017)20902060101081942
Chu (2018)18531804553621387

1 as available in the article and/or in supplementary material
2 uniprot mapping returns all protein isoforms as one entry

The compilation of older studies can be retrieved from the Red Blood Cell Collection database.

The data and differentiation stages presented below come from the proteomic study and analysis performed by our partners of the GReX consortium, more details are available in their published work.

No sequence conservation computed yet.
Protein sequence (FASTA)
Protein coevolution profile (FreeContact)
Multiple Sequence Alignment (Muscle)

This protein is annotated as membranous in Gene Ontology, is annotated as membranous in UniProt.


Interpro domains
Total structural coverage: 100%
Model score: 0
No model available.

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The reference OMIM entry for this protein is 613532

Ras-associated protein rab8b; rab8b

DESCRIPTION

RAB proteins, like RAB8B, are low molecular mass monomeric GTPases that localize on the cytoplasmic surfaces of distinct membrane-bound organelles. RAB proteins function in intracellular vesicle transport by aiding in the docking and/or fusion of vesicles with their target membranes (summary by Chen et al., 1997).

CLONING

Using degenerative primers to amplify RAB cDNAs from a human pigmented melanoma cell line, Chen et al. (1997) obtained a partial RAB8B clone encoding the highly conserved region encompassing GTP-binding domains II and III. Within this region, RAB8B shares complete amino acid identity with rat Rab8b and 96% identity with human RAB8 (RAB8A; 165040). By RT-PCR of rat tissues, Lau and Mruk (2003) found highest Rab8b expression in brain and testis, with lower expression in heart, kidney, and spleen. Rab8b was also expressed in Sertoli and germ cells, and expression increased in these cells during maturation. Expression of Rab8b increased in testis during initiation of meiosis, when secondary spermatocytes first appear. Immunohistochemical analysis of adult rat testis detected Rab8b in the basal compartment in all stages of the spermatogenic cycle. In cultured Sertoli cells, Rab8b associated with membrane junctions. Western blot analysis detected rat Rab8b at an apparent molecular mass of 24 kD. Heidrych et al. (2008) noted that mouse Rab8b and Rab8a share about 80% amino acid identity, with highest conservation in their N-terminal domains. RT-PCR detected Rab8b expression in both immature and mature mouse cochlear hair cells. Rab8b was also expressed in rodent brain and in colonic epithelial cells.

GENE FUNCTION

Throughout spermatogenesis, germ cells migrate from the basal to the adluminal compartment while remaining attached to Sertoli cells via actin (see 102560)-based adherens and intermediate filament-based anchoring junctions. Lau and Mruk (2003) found that when rat Sertoli cells were cultured at high density, or when germ cells were cocultured with Sertoli cells, expression of Rab8b increased during cell-cell junction assembly. In Sertoli cells, expression declined to basal level after junctions were assembled. Germ cell-conditioned medium stimulated Rab8b expression in Sertoli cells in a dose-dependent and androgen-independent manner. Chemical crosslinking and coimmunoprecipitation analysis revealed that Rab8b associated with actin, vimentin (VIM; 193060), alpha-tubulin (see 602529), beta-tubulin (TUBB; 191130), E-cadherin (CDH1; 192090), and gamma-catenin (JUP; 173325), but not with several other cytoskeletal components, including gamma-tubulin (see 191135). Lau and Mruk (2003) concluded that RAB8B may participate in cell junction dynamics, but that it is unlikely to be required for junction maintenance. Using immunofluorescence microscopy and reciprocal coimmunoprecipitation analysis, Heidrych et al. (2008) showed that Rab8b colocalized and interacted directly with otoferlin (OTOF; 603681) in mouse cochlear inner hair cells and in transfected cell lines. They proposed that otoferlin-Rab8b complexes may be involved in recycling endosomes and in basolateral vesicle transport.

MAPPING

Hartz (2010) mapped the RAB8B gene to chromosome 15q22.2 based on an alignment of the RAB8B sequence (GenBank GENBANK AB038995) with the genomic sequence (GRCh37). ... More on the omim web site

Subscribe to this protein entry history

Feb. 2, 2018: Protein entry updated
Automatic update: Uniprot description updated

Dec. 19, 2017: Protein entry updated
Automatic update: Uniprot description updated

March 16, 2016: Protein entry updated
Automatic update: OMIM entry 613532 was added.