Cingulin

Cingulin (CGN; from the Latin cingere "to form a belt around") is a cytosolic protein encoded by the CGN gene in humans localized at tight junctions (TJs) of vertebrate epithelial and endothelial cells.

Cingulin (CGN; from the Latin cingere "to form a belt around") is a cytosolic protein encoded by the CGN gene in humans localized at tight junctions (TJs) of vertebrate epithelial and endothelial cells. == Structure & interactions== Cingulin is a homodimer, each subunit containing a N-terminal globular "head" domain, a long α-helical coiled-coil "rod" domain and a small globular C-terminal "tail" region. This organization is highly conserved throughout vertebrates. However, cingulin homologs have not been detected in invertebrates. In vitro, cingulin can bind to and bundle actin filaments, and interact with myosin II and several TJ proteins including ZO-1, ZO-2, ZO-3, paracingulin and occludin. Moreover, cingulin forms a complex with JAM-A, a tight junction membrane protein. Most of cingulin protein interactions are through the globular head domain. Cingulin interacts with ZO-1 through an N-terminal ZO-1 interacting motif (ZIM) in its head region. The rod domain is involved in dimerization and interaction with the RhoA activator, GEF-H1. Cingulin has also been found to interact with microtubules (MTs) through the N-terminal head region, and these interactions was regulated by phosphorylation by the adenosine monophosphate-activated protein kinase (AMPK). ==Human diseases== Although cingulin has been involved in regulation of RhoA signaling and gene expression in cultured cells and KO mice, nothing is known about the specific role of cingulin in human diseases. Cingulin expression has been studied in human carcinomas and shown to be expressed in adenocarcinomas and down-regulated in squamous carcinomas. Furthermore, histone deacetylase inhibitors, such as sodium butyrate, strongly upregulate its expression in some cultured cells. Cingulin, as other junctional proteins could be used as a marker of epithelial differentiation, and as a diagnostic marker to distinguish adenocarcinomas from squamous carcinomas.

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