RAB9B

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005764 lysosome	IBA GO_REF:0000033	ACCEPT	Summary: RAB9B localizes to late endosomes and lysosomes as part of its role in retrograde transport from late endosomes to the TGN. IBA annotation is phylogenetically inferred from conserved Rab9 family members. Reason: Rab9 family proteins are established regulators of late endosome-TGN trafficking and localize to late endosomal/lysosomal membranes. This is consistent with UniProt annotation and the deep research review showing Rab9 proteins localize to late endosomes and lysosomes (PMID:21255211, PMID:20937701). Supporting Evidence: PMID:21255211 Rab GTPases regulate membrane trafficking, but details of how Rab GTPases regulate phagosome maturation and how M. tb modulates their localization during inhibiting phagolysosome biogenesis remain elusive. file:human/RAB9B/RAB9B-deep-research-falcon.md model: Edison Scientific Literature
GO:0045335 phagocytic vesicle	IBA GO_REF:0000033	ACCEPT	Summary: RAB9B is recruited to phagosomes, as demonstrated by direct experimental evidence showing recruitment to phagosomes containing S. aureus or M. tuberculosis. Reason: This IBA annotation is supported by direct experimental evidence from PMID:21255211 showing RAB9B localization to phagosomes. UniProt also notes RAB9B is recruited to phagosomes containing bacterial pathogens. Supporting Evidence: PMID:21255211 We compared the localization of 42 distinct Rab GTPases to phagosomes containing either Staphylococcus aureus or M. tb.
GO:0005770 late endosome	IBA GO_REF:0000033	ACCEPT	Summary: RAB9B localizes to late endosomes where it regulates retrograde transport to the TGN. This is the primary site of Rab9 function. Reason: Late endosome localization is the canonical site for Rab9 family function. PMID:8164745 demonstrated selective targeting of prenylated Rab9 protein onto late endosome membranes. This is a core localization for RAB9B. Supporting Evidence: PMID:8164745 Rab9 is localized primarily to late endosomes, where it aids the transport of mannose 6-phosphate receptors to the trans-Golgi network.
GO:0042147 retrograde transport, endosome to Golgi	IBA GO_REF:0000033	ACCEPT	Summary: RAB9B is involved in retrograde transport from endosomes to the trans-Golgi network, mediating recycling of mannose-6-phosphate receptors. Reason: This is the primary biological process for Rab9 family members. Multiple publications demonstrate Rab9 function in late endosome to TGN transport, including CI-M6PR recycling (PMID:8164745, PMID:19490898). Supporting Evidence: PMID:8164745 Rab9 is localized primarily to late endosomes, where it aids the transport of mannose 6-phosphate receptors to the trans-Golgi network. PMID:19490898 RhoBTB3, binds directly to Rab9 GTPase and functions with Rab9 in protein transport from endosomes to the trans Golgi network.
GO:0000166 nucleotide binding	IEA GO_REF:0000043	ACCEPT	Summary: RAB9B binds nucleotides (GDP and GTP) as part of its GTPase cycle. Reason: This is a correct but general annotation. RAB9B is a GTPase that cycles between GDP and GTP-bound states. More specific annotations (GTP binding, GDP binding, GTPase activity) are also present. This IEA annotation from UniProt keyword mapping is acceptable as a parent term.
GO:0003924 GTPase activity	IEA GO_REF:0000002	ACCEPT	Summary: RAB9B has GTPase activity (EC 3.6.5.2), hydrolyzing GTP to GDP as part of its regulatory cycle. Reason: RAB9B is assigned EC 3.6.5.2 (small monomeric GTPase) in UniProt. Crystal structure (PDB:2OCB) shows RAB9B bound to GTP analog and Mg2+, confirming the active site architecture for GTP hydrolysis. This is a core molecular function. Supporting Evidence: UniProt:Q9NP90 Reaction=GTP + H2O = GDP + phosphate + H(+);
GO:0003925 G protein activity	IEA GO_REF:0000120	ACCEPT	Summary: RAB9B functions as a small G protein, cycling between GDP and GTP-bound states to regulate membrane trafficking. Reason: G protein activity accurately describes RAB9B function. Rab proteins are small monomeric G proteins that act as molecular switches in vesicular trafficking. This is supported by experimental evidence (PMID:8164745).
GO:0005525 GTP binding	IEA GO_REF:0000120	ACCEPT	Summary: RAB9B binds GTP in its active state, enabling effector recruitment. Reason: Crystal structure (PDB:2OCB) directly shows RAB9B binding a GTP analog. Multiple publications demonstrate GTP-dependent effector binding (PMID:20048159, PMID:19490898). This is a core molecular function. Supporting Evidence: PMID:20048159 An interaction screen reveals a specific and strong interaction of BLOC-3 with the GTP-bound form of the endosomal GTPase, Rab9.
GO:0005886 plasma membrane	IEA GO_REF:0000044	KEEP AS NON CORE	Summary: IEA annotation suggesting plasma membrane localization based on UniProt subcellular location vocabulary mapping. Reason: While RAB9B may associate with plasma membrane through its prenylation, the primary localization is to late endosomes and phagosomes. Plasma membrane localization is not the core functional location. The TAS annotation from Reactome (neutrophil degranulation pathway) provides some support, but this is not the primary site of RAB9B function.
GO:0015031 protein transport	IEA GO_REF:0000043	ACCEPT	Summary: RAB9B is involved in protein transport, specifically in retrograde transport from endosomes to TGN. Reason: This is a correct parent term for the more specific process of endosome-to-Golgi retrograde transport. RAB9B regulates transport of mannose-6-phosphate receptors (PMID:8164745, PMID:19490898).
GO:0016787 hydrolase activity	IEA GO_REF:0000043	ACCEPT	Summary: RAB9B has hydrolase activity through its GTPase function. Reason: This is a correct but very general parent term for GTPase activity. RAB9B hydrolyzes GTP to GDP (EC 3.6.5.2). More specific annotations (GTPase activity) are also present.
GO:0030670 phagocytic vesicle membrane	IEA GO_REF:0000044	ACCEPT	Summary: RAB9B localizes to phagocytic vesicle membranes through its C-terminal prenylation and membrane targeting. Reason: This annotation is consistent with the IDA evidence from PMID:21255211 showing RAB9B localization to phagosomes. UniProt notes the protein is recruited to phagosomes and localizes via lipid anchor to the cytoplasmic side of membranes. Supporting Evidence: UniProt:Q9NP90 Note=Recruited to phagosomes containing S.aureus or M.tuberculosis.
GO:0031090 organelle membrane	IEA GO_REF:0000117	ACCEPT	Summary: RAB9B localizes to organelle membranes including late endosome and phagosome membranes. Reason: This is a general parent term that correctly captures RAB9B membrane localization. More specific CC annotations (late endosome, phagocytic vesicle membrane) are also present.
GO:0031410 cytoplasmic vesicle	IEA GO_REF:0000043	ACCEPT	Summary: RAB9B localizes to cytoplasmic vesicles, including late endosomes and transport vesicles. Reason: This is a correct parent term for RAB9B localization to late endosomes and phagosomes, which are types of cytoplasmic vesicles. The IEA from UniProt keyword mapping is appropriate.
GO:0032482 Rab protein signal transduction	IEA GO_REF:0000002	ACCEPT	Summary: RAB9B participates in Rab-mediated signal transduction through its GTPase cycle and effector recruitment. Reason: This annotation accurately describes RAB9B function as a Rab GTPase that transduces signals through cycling between GDP and GTP-bound states. IEA from InterPro domain mapping is appropriate.
GO:0045335 phagocytic vesicle	IEA GO_REF:0000120	ACCEPT	Summary: Duplicate annotation for phagocytic vesicle localization via combined automated annotation methods. Reason: This is a duplicate of the IBA annotation for the same term. Both are acceptable as they are supported by experimental evidence (PMID:21255211).
GO:0042802 identical protein binding	IEA GO_REF:0000107	UNDECIDED	Summary: IEA annotation suggesting RAB9B self-interaction, transferred from mouse ortholog via Ensembl Compara. Reason: The annotation is transferred from mouse RAB9B (Q8BHH2). While some Rab GTPases may dimerize, there is no direct evidence cited for RAB9B self-interaction. This should be verified experimentally before full acceptance.
GO:0003925 G protein activity	IDA PMID:8164745 Membrane targeting of the small GTPase Rab9 is accompanied b...	ACCEPT	Summary: Direct experimental evidence for RAB9B G protein activity from the Soldati et al. 1994 study demonstrating membrane targeting and nucleotide exchange. Reason: PMID:8164745 demonstrated that Rab9 targeting to late endosomes is accompanied by nucleotide exchange, which is the hallmark of G protein function. This provides experimental support for G protein activity. Supporting Evidence: PMID:8164745 Here we describe the reconstitution of the selective targeting of prenylated Rab9 protein onto late endosome membranes and show that this process is accompanied by endosome-triggered nucleotide exchange.
GO:0006898 receptor-mediated endocytosis	IDA PMID:8164745 Membrane targeting of the small GTPase Rab9 is accompanied b...	MODIFY	Summary: Annotation suggesting RAB9B involvement in receptor-mediated endocytosis based on PMID:8164745. Reason: PMID:8164745 focuses on Rab9 role in late endosome to TGN transport (recycling mannose-6-phosphate receptors), not receptor-mediated endocytosis per se. The term GO:0042147 (retrograde transport, endosome to Golgi) is more accurate. RAB9B functions in retrograde trafficking, not the internalization step of endocytosis. Proposed replacements: retrograde transport, endosome to Golgi Supporting Evidence: PMID:8164745 Rab9 is localized primarily to late endosomes, where it aids the transport of mannose 6-phosphate receptors to the trans-Golgi network.
GO:0005515 protein binding	IPI PMID:20048159 Assembly of the biogenesis of lysosome-related organelles co...	REMOVE	Summary: Annotation for protein binding based on interaction with HPS4/BLOC-3 complex. Reason: GO:0005515 (protein binding) is uninformative as it provides no specificity about the molecular function. The underlying evidence from PMID:20048159 shows RAB9B interaction with HPS4 and BLOC-3 complex, which could support a more specific annotation like effector binding if such a term exists, but generic protein binding should be avoided. Supporting Evidence: PMID:20048159 An interaction screen reveals a specific and strong interaction of BLOC-3 with the GTP-bound form of the endosomal GTPase, Rab9. This interaction is mediated by HPS4 and the switch I and II regions of Rab9.
GO:0005886 plasma membrane	TAS Reactome:R-HSA-6798743	KEEP AS NON CORE	Summary: TAS annotation from Reactome neutrophil degranulation pathway (R-HSA-6798743) suggesting plasma membrane localization. Reason: The Reactome pathway involves exocytosis of secretory granule membrane proteins during neutrophil degranulation. While RAB9B may transiently associate with plasma membrane during this process, this is not its primary localization. The core sites are late endosomes and phagosomes.
GO:0030667 secretory granule membrane	TAS Reactome:R-HSA-6798743	KEEP AS NON CORE	Summary: TAS annotation from Reactome suggesting RAB9B localization to secretory granule membrane during neutrophil degranulation. Reason: This annotation is from the Reactome neutrophil degranulation pathway. While potentially valid in neutrophils, this is not the core localization of RAB9B. The primary sites are late endosomes and phagosomes for the canonical retrograde transport function.
GO:0005829 cytosol	TAS Reactome:R-HSA-9706390	ACCEPT	Summary: TAS annotation suggesting cytosolic localization from Reactome pathway R-HSA-9706390 (RHOBTB3 ATPase cycle). Reason: Rab GTPases cycle between membrane-bound (active) and cytosolic (inactive) states. The cytosolic pool is bound to GDI (GDP dissociation inhibitor) in the GDP-bound form. This annotation reflects the inactive cytosolic pool of RAB9B. Supporting Evidence: PMID:8164745 A fraction of Rab proteins is present in the cytosol, bound with GDP, complexed to a protein termed GDI.
GO:0045335 phagocytic vesicle	IDA PMID:21255211 Rab GTPases regulating phagosome maturation are differential...	ACCEPT	Summary: Direct experimental evidence showing RAB9B localization to phagosomes containing bacterial pathogens. Reason: PMID:21255211 directly demonstrated that RAB9B is recruited to phagosomes containing S. aureus and M. tuberculosis. This is high-quality IDA evidence for phagosomal localization. UniProt cites this as experimental evidence. Supporting Evidence: PMID:21255211 We compared the localization of 42 distinct Rab GTPases to phagosomes containing either Staphylococcus aureus or M. tb. UniProt:Q9NP90 Note=Recruited to phagosomes containing S.aureus or M.tuberculosis.
GO:0019003 GDP binding	IDA PMID:20937701 Family-wide characterization of the DENN domain Rab GDP-GTP ...	ACCEPT	Summary: Direct experimental evidence for GDP binding from the Yoshimura et al. 2010 study characterizing DENN domain Rab GEFs. Reason: PMID:20937701 used GDP-releasing assays to characterize DENN GEFs, which directly demonstrates that Rab9 proteins bind GDP. This is the inactive state of the protein. Combined with GTP binding, this reflects the nucleotide cycling of RAB9B. Supporting Evidence: PMID:20937701 DENND2 GEFs target to actin filaments and control Rab9-dependent trafficking of mannose-6-phosphate receptor to lysosomes.
GO:0005515 protein binding	IPI PMID:19490898 RhoBTB3: a Rho GTPase-family ATPase required for endosome to...	REMOVE	Summary: Annotation for protein binding based on interaction with RhoBTB3. Reason: GO:0005515 (protein binding) is uninformative. The evidence from PMID:19490898 shows specific interaction between RAB9B and RhoBTB3, an ATPase required for endosome to Golgi transport. Generic protein binding should be removed in favor of more informative annotations. Supporting Evidence: PMID:19490898 RhoBTB3, binds directly to Rab9 GTPase and functions with Rab9 in protein transport from endosomes to the trans Golgi network.

Gene Description

Existing Annotations Review

Core Functions

RAB9B is a small monomeric GTPase (EC 3.6.5.2) that hydrolyzes GTP to GDP. Crystal structure (PDB:2OCB) confirms GTP analog binding with Mg2+ cofactor. This enzymatic activity drives the nucleotide cycling that controls RAB9B membrane targeting and effector recruitment.

RAB9B binds GTP in its active state, enabling recruitment of effector proteins including BLOC-3, RhoBTB3, TIP47, and NDE1. Crystal structure demonstrates GTP analog binding (PDB:2OCB). GTP-dependent effector binding is demonstrated in PMID:20048159 and PMID:19490898.

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