Alternative titles; symbols
HGNC Approved Gene Symbol: ITSN1
Cytogenetic location: 21q22.11 Genomic coordinates (GRCh38) : 21:33,642,501-33,899,861 (from NCBI)
Intersectin-1 is an evolutionarily conserved, multidomain protein that functions in clathrin-associated endocytosis and as a mediator of MAPK signaling pathways (Tsyba et al., 2004).
Chen and Antonarakis (1997) used exon trapping to identify portions of genes on human chromosome 21. A BLAST search of databases revealed that 1 trapped sequence was identical to a region of the GenBank entry for the Src homology 3 (SH3) domain-containing gene SH3D1A, formerly called SH3P17 by Sparks et al. (1996).
By Alu-splice PCR, Pucharcos et al. (1999) trapped 2 exons and subsequently identified the full-length cDNA of the ITSN gene. The gene has the potential to code for at least 2 different protein isoforms by alternative splicing (ITSN-L and ITSN-S). Intersectin exists with a high degree of similarity in flies, frogs, and mammals, suggesting a conserved role in higher eukaryotes. ITSN mRNAs were detected in all adult and fetal tissues tested in human and mouse, with the longer isoform present in the brain. In situ hybridization studies in the developing mouse brain showed ITSN expression in both proliferating and differentiating neurons. Pucharcos et al. (1999) determined the genomic structure of ITSN using chromosome 21 sequences deposited in the public databases. The protein contains several known motifs which implicate ITSN in clathrin-mediated endocytosis and synaptic vesicle recycling. The expression pattern of intersectin in mouse brain, its presumed function, and its overexpression in brains from Down syndrome patients, suggested intersectin may contribute in a gene dosage-dependent manner to some of the abnormalities of Down syndrome.
Pucharcos et al. (2000) determined by Western blot analysis that the short and long isoforms of ITSN1 encode 138- and 195-kD proteins, respectively, as predicted. Immunofluorescence microscopy demonstrated sparse punctate expression throughout the cytoplasm for both ITSN1 and ITSN2 (604464), with ITSN1 having a more marked perinuclear pattern and a concentration in Golgi-like structures.
Tsyba et al. (2004) noted that ITSN1 has a complex domain structure. Both ITSN1 isoforms have 2 N-terminal Eps15 (600051) homology (EH) domains, followed by a coiled-coil domain and 5 Src (190090) homology-3 (SH3) domains. In addition, the long isoform has a C-terminal extension containing a Dbl (311030) homology (DH), or RhoGEF (see 601855), domain, a pleckstrin (173570) homology (PH) domain, and a putative calcium-interaction domain. Tsyba et al. (2004) identified 8 additional alternative splicing events that affect mouse and human ITSN1 transcripts. These splicing events decrease the EH domain spacing, introduce an insertion in the first SH3 domain, delete the DH domain, or create frameshifts that truncate the open reading frames at several points. Tsyba et al. (2004) concluded that alternative splicing contributes to the regulation of ITSN1 protein functions by creating diversity in domain composition among protein isoforms.
Pucharcos et al. (2000) found that overexpression of either of the ITSN2 isoforms or ITSN1 resulted in the inhibition of transferrin uptake and the blockage of clathrin-mediated endocytosis.
Morphologic changes in neuronal dendritic spines are believed to be caused by dynamic regulation of actin polymerization. Irie and Yamaguchi (2002) found that the EphB2 receptor tyrosine kinase (600997) physically associates with intersectin-1 in cooperation with the actin-regulating protein N-WASP (605056), which in turn activates the Rho family GTPase Cdc42 (116952) and spine morphogenesis.
He et al. (2007) showed that mammalian Wnk1 (605232) and Wnk4 (601844) interacted with Itsn1 and that these interactions were crucial for stimulation of Romk1 (KCNJ1; 600359) endocytosis. Stimulation of Romk1 endocytosis by Wnk1 and Wnk4 required their proline-rich motifs, but it did not require their kinase activities. Pseudohypoaldosteronism II (PHA2B; 614491)-causing mutations in Wnk4 enhanced the interactions of Wnk4 with Itsn1 and Romk1, leading to increased endocytosis of Romk1.
Tsyba et al. (2004) determined that the ITSN1 gene contains 41 exons. Exon 1 is noncoding, and the initiator methionine is located in exon 2.
By hybridization and PCR, Chen and Antonarakis (1997) mapped the SH3D1A gene to YACs and cosmids within 21q22.1-q22.2, between DNA markers D21S319 and D21S65.
Chen, H., Antonarakis, S. E. The SH3D1A gene maps to human chromosome 21q22.1-q22.2. Cytogenet. Cell Genet. 78: 213-215, 1997. [PubMed: 9465890] [Full Text: https://doi.org/10.1159/000134659]
He, G., Wang, H.-R., Huang, S.-K., Huang, C.-L. Intersectin links WNK kinases to endocytosis of ROMK1. J. Clin. Invest. 117: 1078-1087, 2007. [PubMed: 17380208] [Full Text: https://doi.org/10.1172/JCI30087]
Irie, F., Yamaguchi, Y. EphB receptors regulate dendritic spine development via intersectin, Cdc42 and N-WASP. Nature Neurosci. 5: 1117-1118, 2002. [PubMed: 12389031] [Full Text: https://doi.org/10.1038/nn964]
Pucharcos, C., Estivill, X., de la Luna, S. Intersectin 2, a new multimodular protein involved in clathrin-mediated endocytosis. FEBS Lett. 478: 43-51, 2000. [PubMed: 10922467] [Full Text: https://doi.org/10.1016/s0014-5793(00)01793-2]
Pucharcos, C., Fuentes, J.-J., Casas, C., de la Luna, S., Alcantara, S., Arbones, M. L., Soriano, E., Estivill, X., Prichard, M. Alu-splice cloning of human intersectin (ITSN), a putative multivalent binding protein expressed in proliferating and differentiating neurons and overexpressed in Down syndrome. Europ. J. Hum. Genet. 7: 704-712, 1999. [PubMed: 10482960] [Full Text: https://doi.org/10.1038/sj.ejhg.5200356]
Sparks, A. B., Hoffman, N. G., McConnell, S. J., Fowlkes, D. M., Kay, B. K. Cloning of ligand targets: systematic isolation of SH3 domain-containing proteins. Nature Biotech. 14: 741-744, 1996. [PubMed: 9630982] [Full Text: https://doi.org/10.1038/nbt0696-741]
Tsyba, L., Skrypkina, I., Rynditch, A., Nikolaienko, O., Ferenets, G., Fortna, A., Gardiner, K. Alternative splicing of mammalian intersectin 1: domain associations and tissue specificities. Genomics 84: 106-113, 2004. [PubMed: 15203208] [Full Text: https://doi.org/10.1016/j.ygeno.2004.02.005]