Discs large homolog 1 (DLG1), also known as synapse-associated protein 97 or SAP97, is a scaffold protein that in humans is encoded by the SAP97 gene.

Protein DLG1 PDB 1iu0.png
Available structures
PDBOrtholog search: PDBe RCSB
AliasesDLG1, DLGH1, SAP-97, SAP97, dJ1061C18.1.1, hdlg, B130052P05Rik, E-dlg/SAP97, mKIAA4187, discs large homolog 1, scribble cell polarity complex component, discs large MAGUK scaffold protein 1
External IDsOMIM: 601014 MGI: 107231 HomoloGene: 20869 GeneCards: DLG1
RefSeq (mRNA)
RefSeq (protein)
Location (UCSC)Chr 3: 197.04 – 197.3 MbChr 16: 31.66 – 31.88 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

SAP97 is a mammalian MAGUK-family member protein that is similar to the Drosophila protein Dlg1 (the protein is alternatively referred to as hDlg1, and the human gene is DLG1). SAP97 is expressed throughout the body in epithelial cells. In the brain it is involved in the trafficking of ionotropic receptors from the endoplasmic reticulum to the plasma membrane, and may be involved in the trafficking AMPAR during synaptic plasticity.


SAP97 is expressed throughout the body in epithelial cells, including the kidney and brain.[5] There is some evidence that SAP97 regulates cell-to-cell adhesion during cell death, and may interact with HPV. In the brain, SAP97's function is involved in the trafficking of transmembrane receptors from the ER to the plasma membrane.[6]

SAP97's function has been investigated by reducing its expression by knockout or increasing its expression heterologously. Mice in which the SAP97 gene has been knocked out die perinatally, have a cleft palate, and deficiencies in renal function.[7][8] Overexpression of SAP97 in mammalian neurons leads to increased synaptic strength.[9]

Clinical significanceEdit

Mutations in DLG1 are associated to Crohn's Disease.[10]

three PDZ domains, an SH3 domain, hook domain, I3 domain, and finally an inactive guanylate kinase (GK) domain.  Each of these domains has specific interacting partners that help define SAP97's unique function.

The n-terminal of SAP97 can be alternatively spliced to contain a double-cysteine/palmitoylation site (α-isoform), or an L27 domain (β-isoform. The L27 domain is involved in SAP97 oligomerization with other SAP97 molecules, CASK, and other L27-domain-containing proteins.[11] There is also a myosin VI binding site near n-terminal which may be involved in the internalization of AMPAR.[12][13]

Each of SAP97's PDZ domains have different binding partners, including the AMPAR subunit GluR1[14][15] for the first PDZ domain, and neuroligin for the last. SAP97's I3 domain is unique to SAP97 among the MAGUK family, and is known to regulate the post-synaptic localization of SAP97[9] and to bind the protein 4.1N. The GK domain allows SAP97 to bind to GKAP/SAPAP-family proteins.


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000075711 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000022770 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. ^ Müller BM, Kistner U, Veh RW, Cases-Langhoff C, Becker B, Gundelfinger ED, Garner CC (Mar 1995). "Molecular characterization and spatial distribution of SAP97, a novel presynaptic protein homologous to SAP90 and the Drosophila discs-large tumor suppressor protein". The Journal of Neuroscience. 15 (3 Pt 2): 2354–66. doi:10.1523/JNEUROSCI.15-03-02354.1995. PMC 6578138. PMID 7891172.
  6. ^ Sans N, Racca C, Petralia RS, Wang YX, McCallum J, Wenthold RJ (Oct 2001). "Synapse-associated protein 97 selectively associates with a subset of AMPA receptors early in their biosynthetic pathway". The Journal of Neuroscience. 21 (19): 7506–16. doi:10.1523/JNEUROSCI.21-19-07506.2001. PMC 6762903. PMID 11567040.
  7. ^ Caruana G, Bernstein A (Mar 2001). "Craniofacial dysmorphogenesis including cleft palate in mice with an insertional mutation in the discs large gene". Molecular and Cellular Biology. 21 (5): 1475–83. doi:10.1128/MCB.21.5.1475-1483.2001. PMC 86693. PMID 11238884.
  8. ^ Mahoney ZX, Sammut B, Xavier RJ, Cunningham J, Go G, Brim KL, Stappenbeck TS, Miner JH, Swat W (Dec 2006). "Discs-large homolog 1 regulates smooth muscle orientation in the mouse ureter". Proceedings of the National Academy of Sciences of the United States of America. 103 (52): 19872–7. doi:10.1073/pnas.0609326103. PMC 1750896. PMID 17172448.
  9. ^ a b Rumbaugh G, Sia GM, Garner CC, Huganir RL (Jun 2003). "Synapse-associated protein-97 isoform-specific regulation of surface AMPA receptors and synaptic function in cultured neurons". The Journal of Neuroscience. 23 (11): 4567–76. doi:10.1523/JNEUROSCI.23-11-04567.2003. PMC 6740810. PMID 12805297.
  10. ^ Xu S, Zhou F, Tao J, Song L, Ng SC, Wang X, Chen L, Yi F, Ran Z, Zhou R, Xia B (2014). "Exome sequencing identifies DLG1 as a novel gene for potential susceptibility to Crohn's disease in a Chinese family study". PLOS ONE. 9 (6): e99807. doi:10.1371/journal.pone.0099807. PMC 4061034. PMID 24937328.
  11. ^ Lee S, Fan S, Makarova O, Straight S, Margolis B (Mar 2002). "A novel and conserved protein-protein interaction domain of mammalian Lin-2/CASK binds and recruits SAP97 to the lateral surface of epithelia". Molecular and Cellular Biology. 22 (6): 1778–91. doi:10.1128/MCB.22.6.1778-1791.2002. PMC 135599. PMID 11865057.
  12. ^ Wu H, Nash JE, Zamorano P, Garner CC (Aug 2002). "Interaction of SAP97 with minus-end-directed actin motor myosin VI. Implications for AMPA receptor trafficking". The Journal of Biological Chemistry. 277 (34): 30928–34. doi:10.1074/jbc.M203735200. PMID 12050163.
  13. ^ Osterweil E, Wells DG, Mooseker MS (Jan 2005). "A role for myosin VI in postsynaptic structure and glutamate receptor endocytosis". The Journal of Cell Biology. 168 (2): 329–38. doi:10.1083/jcb.200410091. PMC 2171578. PMID 15657400.
  14. ^ Leonard AS, Davare MA, Horne MC, Garner CC, Hell JW (Jul 1998). "SAP97 is associated with the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor GluR1 subunit". The Journal of Biological Chemistry. 273 (31): 19518–24. doi:10.1074/jbc.273.31.19518. PMID 9677374.
  15. ^ Cai C, Coleman SK, Niemi K, Keinänen K (Aug 2002). "Selective binding of synapse-associated protein 97 to GluR-A alpha-amino-5-hydroxy-3-methyl-4-isoxazole propionate receptor subunit is determined by a novel sequence motif". The Journal of Biological Chemistry. 277 (35): 31484–90. doi:10.1074/jbc.M204354200. PMID 12070168.
| volume = 25 | issue = 6 | pages = 542–53 | date = Jun 2003 | pmid = 12766944 | doi = 10.1002/bies.10286 }}

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