[CSKP_HUMAN] Defects in CASK are the cause of mental retardation and microcephaly with pontine and cerebellar hypoplasia (MICPCH) [MIM:300749]. A disorder characterized by significantly below average general intellectual functioning associated with impairments in adaptative behavior and manifested during the developmental period. Patients with mental retardation X-linked CASK-related can manifest a severe phenotype consisting of severe intellectual deficit, congenital or postnatal microcephaly, disproportionate brainstem and cerebellar hypoplasia. A milder phenotype consists of mental retardation alone or associated with nystagmus. Defects in CASK are the cause of FG syndrome type 4 (FGS4) [MIM:300422]. FG syndrome (FGS) is an X-linked disorder characterized by mental retardation, relative macrocephaly, hypotonia and constipation.
[CSKP_HUMAN] Multidomain scaffolding protein with a role in synaptic transmembrane protein anchoring and ion channel trafficking. Contributes to neural development and regulation of gene expression via interaction with the transcription factor TRB1. Binds to cell-surface proteins, including amyloid precursor protein, neurexins and syndecans. May mediate a link between the extracellular matrix and the actin cytoskeleton via its interaction with syndecan and with the actin/spectrin-binding protein 4.1.
CASK is a member of the membrane-associated guanylate kinases (MAGUK) homologs, a family of proteins that scaffold protein complexes at particular regions of the plasma membrane by utilizing multiple protein-binding domains. The GK domain of MAGUKs, which shares high similarity in amino acid sequence with yeast guanylate kinase (yGMPK), is the least characterized MAGUK domain both in structure and function. In addition to its scaffolding function, the GK domain of hCASK has been shown to be involved in transcription regulation. Here we report the crystal structure of the GK domain of human CASK (hCASK-GK) at 1.3-A resolution. The structure rationalizes the inability of the GK domain to catalyze phosphoryl transfer and strongly supports its new function as a protein-binding module. Comparison of the hCASK-GK structure with the available crystal structures of yGMPK provides insight into possible conformational changes that occur in hCASK upon GMP binding. These conformational changes may act to regulate hCASK-GK function in a nucleotide-dependent manner.
Structural basis for nucleotide-dependent regulation of membrane-associated guanylate kinase-like domains.,Li Y, Spangenberg O, Paarmann I, Konrad M, Lavie A J Biol Chem. 2002 Feb 8;277(6):4159-65. Epub 2001 Nov 29. PMID:11729206
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
↑ Najm J, Horn D, Wimplinger I, Golden JA, Chizhikov VV, Sudi J, Christian SL, Ullmann R, Kuechler A, Haas CA, Flubacher A, Charnas LR, Uyanik G, Frank U, Klopocki E, Dobyns WB, Kutsche K. Mutations of CASK cause an X-linked brain malformation phenotype with microcephaly and hypoplasia of the brainstem and cerebellum. Nat Genet. 2008 Sep;40(9):1065-7. doi: 10.1038/ng.194. PMID:19165920 doi:10.1038/ng.194
↑ Piluso G, D'Amico F, Saccone V, Bismuto E, Rotundo IL, Di Domenico M, Aurino S, Schwartz CE, Neri G, Nigro V. A missense mutation in CASK causes FG syndrome in an Italian family. Am J Hum Genet. 2009 Feb;84(2):162-77. doi: 10.1016/j.ajhg.2008.12.018. Epub 2009, Feb 5. PMID:19200522 doi:10.1016/j.ajhg.2008.12.018
↑ Li Y, Spangenberg O, Paarmann I, Konrad M, Lavie A. Structural basis for nucleotide-dependent regulation of membrane-associated guanylate kinase-like domains. J Biol Chem. 2002 Feb 8;277(6):4159-65. Epub 2001 Nov 29. PMID:11729206 doi:10.1074/jbc.M110792200