{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nRAP1GDS1 (also known as SmgGDS) is an atypical guanine nucleotide exchange factor and molecular chaperone that plays a central role in the regulation of small GTPases. Rather than functioning solely as a canonical exchange factor, RAP1GDS1 modulates the prenylation and membrane trafficking of C‐terminal polybasic GTPases in the Ras and Rho families. Structural and biochemical studies have revealed that the protein exists as distinct splice variants (e.g., SmgGDS‐607 and SmgGDS‐558), each displaying unique affinities for non‐prenylated versus prenylated substrates and using nontraditional mechanisms to promote GDP dissociation or to sequester substrates prior to prenylation. These findings have been supported by crystal structures that detail an armadillo‐repeat fold and discrete charged regions that govern recognition of both the polybasic regions and prenyl moieties of target proteins."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "4"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn the context of oncogenesis, RAP1GDS1 has emerged as a critical regulator of cell proliferation, cell cycle progression, and migration. Elevated expression of RAP1GDS1 isoforms in several cancers—including breast cancer and non‐small cell lung carcinoma—correlates with enhanced RhoA/RhoC activity, dysregulated NF‑κB transcription, and overall aggressive tumor phenotypes. Moreover, RAP1GDS1 can be competitively bound by tumor‐suppressive proteins such as DiRas1, which interferes with its ability to deliver oncogenic GTPases to downstream effectors. These activities support the notion that RAP1GDS1 is not only instrumental for proper prenylation and subcellular localization of its targets but also represents a promising therapeutic target to counteract malignant signaling."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "5", "end_ref": "9"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nAdditional studies have underscored RAP1GDS1’s role in fine-tuning the kinetics of prenylation and the spatial localization of small GTPases, thereby affecting diverse signaling pathways such as those governing mitochondrial dynamics and mTORC1 activation. Inhibition of RAP1GDS1 activity alters the access of substrates to prenyltransferases, modulates product release, and can impact cytosolic retention versus membrane association of key regulators like RHEB. These regulatory functions are further implicated in promoting oncogenic growth by ensuring proper subcellular distribution of signaling molecules, and have opened novel avenues for targeting RAP1GDS1 in cancers characterized by aberrant mTORC1 activity and other dysregulated small GTPase pathways."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "10", "end_ref": "16"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Tracy J Berg, Adam J Gastonguay, Ellen L Lorimer, et al. 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"}, {"type": "b", "children": [{"type": "t", "text": "Structure-based analysis of the guanine nucleotide exchange factor SmgGDS reveals armadillo-repeat motifs and key regions for activity and GTPase binding."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "J Biol Chem (2017)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1074/jbc.M117.792556"}], "href": "https://doi.org/10.1074/jbc.M117.792556"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "28630045"}], "href": "https://pubmed.ncbi.nlm.nih.gov/28630045"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "Abdulaziz Asiri, Essra Aloyouni, Muhammad Umair, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Mutated RAP1GDS1 causes a new syndrome of dysmorphic feature, intellectual disability & speech delay."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Ann Clin Transl Neurol (2020)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1002/acn3.51059"}], "href": "https://doi.org/10.1002/acn3.51059"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "32431071"}], "href": "https://pubmed.ncbi.nlm.nih.gov/32431071"}]}, {"type": "r", "ref": 5, "children": [{"type": "t", "text": "Andrew D Hauser, Carmen Bergom, Nathan J Schuld, et al. "}, {"type": "b", "children": [{"type": "t", "text": "The SmgGDS splice variant SmgGDS-558 is a key promoter of tumor growth and RhoA signaling in breast cancer."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Mol Cancer Res (2014)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1158/1541-7786.MCR-13-0362"}], "href": "https://doi.org/10.1158/1541-7786.MCR-13-0362"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "24197117"}], "href": "https://pubmed.ncbi.nlm.nih.gov/24197117"}]}, {"type": "r", "ref": 6, "children": [{"type": "t", "text": "Nathan J Schuld, Jeffrey S Vervacke, Ellen L Lorimer, et al. 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