Alternative titles; symbols
HGNC Approved Gene Symbol: CYTH2
Cytogenetic location: 19q13.33 Genomic coordinates (GRCh38): 19:48,469,369-48,482,314 (from NCBI)
CYTH2 is a guanine nucleotide exchange factor (GEF) for the small GTP-binding protein ARF6 (600464), which is involved in cytoskeletal rearrangement (Torii et al., 2014).
Using a yeast 2-hybrid screen of a T-cell leukemia cell line with the intracellular portion of CD18 (ITGB2; 600065) as bait, Kolanus et al. (1996) isolated a cDNA encoding cytohesin-1 (PSCD1; 182115) and a partial cDNA encoding PSCD2, which they designated cts18.1. Sequence analysis predicted that the PSCD2 fragment is 88% identical to PSCD1. Northern blot analysis revealed broad expression of 2.1- and 6.5-kb PSCD2L transcripts.
Chardin et al. (1996) characterized a protein with a relative molecular mass of 47 kD, which they named ARNO. ARNO contains a central Sec7 domain that promotes guanine nucleotide exchange on the small G protein ARF1 (103180). ARNO also contains an N-terminal coiled-coil motif and a C-terminal pleckstrin homology (PH) domain. The PH domain mediates an enhancement of ARNO exchange activity by negatively charged phospholipid vesicles supplemented with phosphatidylinositol bisphosphate.
Crystal Structure
Mossessova et al. (1998) reported the crystal structure of the catalytic Sec7 homology domain of ARNO, determined at 2.2-angstrom resolution. The Sec7 domain is an elongated, all-helical protein with a distinctive hydrophobic groove that is phylogenetically conserved. Structure-based mutagenesis identified the groove and an adjacent conserved loop as the ARF-interacting surface. The sites of Sec7 domain interaction on ARF1 have subsequently been mapped, by protein footprinting experiments, to the switch 1 and switch 2 GTPase regions, leading to a model for the interaction between ARF GTPases and Sec7 domain exchange factors.
Chardin et al. (1996) found that the exchange activity of ARNO was not inhibited by brefeldin A (BFA), an agent known to block vesicular transport and inhibit the exchange activity on ARF1 in cell extracts. This suggested to the investigators that a regulatory component that is sensitive to brefeldin A associates with ARNO in vivo, possibly through the N-terminal coiled-coil. They proposed that other proteins with a Sec7 domain regulate different members of the ARF family.
Nucleotide dissociation from small G protein-GEF complexes involves transient GDP-bound intermediates. In the case of ARF proteins, small G proteins that regulate membrane traffic in eukaryotic cells, such intermediates can be trapped either by the natural inhibitor brefeldin A or by charge reversal at the catalytic glutamate of the Sec7 domain of their GEFs. Taking advantage of the point mutations that convert the BFA-insensitive Sec7 domain of the human GEF ARNO into a BFA-sensitive GEF, Renault et al. (2003) determined the crystal structure of these intermediates, which showed that membrane recruitment of ARF and nucleotide dissociation are separate reactions stimulated by the Sec7 domain. The reactions proceed through sequential rotations of the Arf-GDP core towards the Sec7 catalytic site, and are blocked by interfacial binding of brefeldin A and unproductive stabilization of GDP by charge reversal.
By immunoblot analysis, Frank et al. (1998) identified ARNO in both cytosolic and membrane fractions. In vitro assays showed that ARNO catalyzes nucleotide exchange on both ARF1 and ARF6. However, immunofluorescence microscopy demonstrated colocalization of ARNO with ARF6 at the plasma membrane and not with ARF1 at the Golgi.
Studying rat hippocampal neurons in culture, Hernandez-Deviez et al. (2002) determined that dendritic arbor development is regulated by complex interactions of ARNO, ARF6, and RAC1 (602048). Activation of ARNO and ARF6 resulted in signaling through RAC1 that suppressed dendritic branching.
White et al. (2010) showed that small interfering RNA (siRNA)-mediated knockdown of IPCEF1 (619948) or GRASP (612027), which bind to the coiled-coil domain of ARNO, prevented association of ARNO with DOCK180 (DOCK1; 601403) and ARNO-induced RAC activation in MCF-7 human breast cancer cells and MDCK cells. White et al. (2010) proposed that scaffold proteins can regulate ARF-dependent processing.
By immunoprecipitation analysis in transfected Caco2 and HEK293 cells, Attar et al. (2012) showed that the C-terminal CRAC domain of CNK3 (617476)/IPCEF1 mediated its interaction with ARNO. Knockdown of CNK3/IPCEF1 via siRNA showed that HGF (142409)-stimulated migration of epithelial cells required CNK3/IPCEF1 for ARF6 activation.
Zhu et al. (2012) showed that the direct, immediate, and disruptive effects of IL1-beta (IL1B; 147720) on endothelial stability in a human in vitro cell model are NF-kappa-B (see 164011)-independent and are instead the result of signaling through the small GTPase ARF6 and its activator ARNO. Moreover, Zhu et al. (2012) showed that ARNO binds directly to the adaptor protein MYD88 (602170), and thus proposed MYD88-ARNO-ARF6 as a proximal IL1-beta signaling pathway distinct from that mediated by NF-kappa-B. Finally, Zhu et al. (2012) showed that SecinH3 (182115), an inhibitor of ARF guanine nucleotide exchange factors such as ARNO, enhances vascular stability and significantly improves outcomes in animal models of inflammatory arthritis and acute inflammation.
Using N1E-115 mouse neuroblastoma cells, Torii et al. (2014) found that Ccdc120 (300947) directed neurite localization of Cyth2 and was required for Arf6 activation during differentiation. Fluorescence-tagged human CCDC120 colocalized with fluorescence-tagged Cyth2 in punctate structures within cell bodies and along extended neurite shafts and growth cones. Cyth2 inhibited ubiquitination and degradation of CCDC120, and CCDC120 targeted Cyth2 to vesicular structures. Knockdown of Ccdc120 in N1E-115 cells via small interfering RNA decreased the total number and length of neurites, dispersed Cyth2 to the cytoplasm, and reduced Arf6 activation. Torii et al. (2014) concluded that both CCDC120 and CYTH2 are required for ARF6 activation and neurite extension.
By radiation hybrid analysis, Kim (1998) mapped the CYTH2 gene to chromosome 19q13.
Attar, M. A., Salem, J. C., Pursel, H. S., Santy, L. C. CNK3 and IPCEF1 produce a single protein that is required for HGF dependent Arf6 activation and migration. Exp. Cell Res. 318: 228-237, 2012. [PubMed: 22085542] [Full Text: https://doi.org/10.1016/j.yexcr.2011.10.018]
Chardin, P., Paris, S., Antonny, B., Robineau, S., Beraud-Dufour, S., Jackson, C. L., Chabre, M. A human exchange factor for ARF contains Sec7- and pleckstrin-homology domains. Nature 384: 481-484, 1996. [PubMed: 8945478] [Full Text: https://doi.org/10.1038/384481a0]
Frank, S., Upender, S., Hansen, S. H., Casanova, J. E. ARNO is a guanine nucleotide exchange factor for ADP-ribosylation factor 6. J. Biol. Chem. 273: 23-27, 1998. [PubMed: 9417041] [Full Text: https://doi.org/10.1074/jbc.273.1.23]
Hernandez-Deviez, D. J., Casanova, J. E., Wilson, J. M. Regulation of dendritic development by the ARF exchange factor ARNO. Nature Neurosci. 5: 623-624, 2002. [PubMed: 12032543] [Full Text: https://doi.org/10.1038/nn865]
Kim, H.-S. Assignment of the human cts18.1 gene PSCD2L to chromosome 19 band q13 using a radiation hybrid mapping panel. Cytogenet. Cell Genet. 83: 43 only, 1998. [PubMed: 9925920] [Full Text: https://doi.org/10.1159/000015163]
Kolanus, W., Nagel, W., Schiller, B., Zeitlmann, L., Godar, S., Stockinger, H., Seed, B. Alpha-L-beta-2 integrin/LFA-1 binding to ICAM-1 induced by cytohesin-1, a cytoplasmic regulatory molecule. Cell 86: 233-242, 1996. [PubMed: 8706128] [Full Text: https://doi.org/10.1016/s0092-8674(00)80095-1]
Mossessova, E., Gulbis, J. M., Goldberg, J. Structure of the guanine nucleotide exchange factor Sec7 domain of human Arno and analysis of the interaction with ARF GTPase. Cell 92: 415-423, 1998. [PubMed: 9476900] [Full Text: https://doi.org/10.1016/s0092-8674(00)80933-2]
Renault, L., Guibert, B., Cherfils, J. Structural snapshots of the mechanism and inhibition of a guanine nucleotide exchange factor. Nature 426: 525-530, 2003. [PubMed: 14654833] [Full Text: https://doi.org/10.1038/nature02197]
Torii, T., Miyamoto, Y., Tago, K., Sango, K., Nakamura, K., Sanbe, A., Tanoue, A., Yamauchi, J. Arf6 guanine nucleotide exchange factor cytohesin-2 binds to CCDC120 and is transported along neurites to mediate neurite growth. J. Biol. Chem. 289: 33887-33903, 2014. [PubMed: 25326380] [Full Text: https://doi.org/10.1074/jbc.M114.575787]
White, D. T., McShea, K. M., Attar, M. A., Santy, L. C. GRASP and IPCEF promote ARF-to-Rac signaling and cell migration by coordinating association of ARNO/cytohesin 2 with Dock180. Molec. Biol. Cell 21: 562-571, 2010. [PubMed: 20016009] [Full Text: https://doi.org/10.1091/mbc.e09-03-0217]
Zhu, W., London, N. R., Gibson, C. C., Davis, C. T., Tong, Z., Sorenson, L. K., Shi, D. S., Guo, J., Smith, M. C. P., Grossmann, A. H., Thomas, K. R., Li, D. Y. Interleukin receptor activates a MYD88-ARNO-ARF6 cascade to disrupt vascular stability. Nature 492: 252-255, 2012. [PubMed: 23143332] [Full Text: https://doi.org/10.1038/nature11603]