Cingulin (CGN; from the Latin cingere “to form a belt around”) is a cytosolic protein encoded by the CGNgene in humans[1][2][3] localized at tight junctions (TJs) of vertebrate epithelial and endothelial cells.
Cingulin was originally discovered at the MRC Laboratory of Molecular Biology (Cambridge, UK) by Dr. Sandra Citi, as a protein present in chicken intestinal epithelial cells, that co-purified with non-muscle myosin II and was specifically localized at tight junctions (zonulae occludentes).[4]
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.[5] This organization is highly conserved throughout vertebrates.[1] 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.[6][7][8] Moreover, cingulin forms a complex with JAM-A, a tight junction membrane protein.[6] 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.[9][10] The rod domain is involved in dimerization and interaction with the RhoA activator, GEF-H1.[11][12][13]
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).[14]
Function
The function of cingulin has been studied by knockout (KO), knockdown (KD) and over-expression approaches. Embryoid bodies derived from embryonic stem cells where one or both cingulin alleles were targeted by homologous recombination show apparently normal tight junctions, but changes in the expression of a large number of genes, including tight junction protein genes (claudin-2, claudin-6, claudin-7 and occludin) and transcription factors (including GATA4).[9] Changes in the expression of claudin-2 and ZO-3 are also observed in cultured kidney cells (MDCK) depleted of cingulin by shRNA.[12]
In 2012, the phenotype of cingulin-knockout mice was described, proving that functional TJ in vivo can be formed in the absence of cingulin.[15] Together with paracingulin, cingulin also was reported to regulate claudin-2 expression through RhoA-dependent and independent mechanisms.[15][16]
The role of cingulin in development has been studied by morpholino.[17] oligonucleotide-mediated depletion in chicken, indicating that cingulin is involved in neural crest development. In early mouse and frog embryos, maternal cingulin is localized in the cell cortex. Through early mouse development, cytocortical cingulin in present from oogenesis (cumulus-oocyte contact sites) until 16-cells morulae stage (apical microvillous zones) during early embryogenesis; then maternal cingulin is degraded by endocytic turn-over from the 32-cells stage. Regarding the zygotic cingulin, it accumulates at the tight junctions from 16-cells stage, 10 hours after ZO-1 assembly. Furthermore, the synthesis of cingulin in early mouse embryos is tissue-specific and it occurs in blastocyst (up-regulated in trophectoderm and down-regulated in inner-cells).[18][19] In Xenopuslaevis embryos, maternal cingulin is recruited to apical cell-cell junctions from 2-cells stage.[20][21]
Homologs
In 2004, a protein homologous to cingulin was discovered and named JACOP (also known as paracingulin, or cingulin-like 1 protein; CGNL1).[13]
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.[11][12][15]
Cingulin expression has been studied in human carcinomas and shown to be expressed in adenocarcinomas and down-regulated in squamous carcinomas.[22][23] Furthermore, histone deacetylase inhibitors, such as sodium butyrate, strongly upregulate its expression in some cultured cells.[24] 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.
References
↑ 1.01.1Citi S, D'Atri F, Parry DA (August 2000). "Human and Xenopus cingulin share a modular organization of the coiled-coil rod domain: predictions for intra- and intermolecular assembly". Journal of Structural Biology. 131 (2): 135–45. doi:10.1006/jsbi.2000.4284. PMID11042084.
↑Nagase T, Kikuno R, Ishikawa KI, Hirosawa M, Ohara O (February 2000). "Prediction of the coding sequences of unidentified human genes. XVI. The complete sequences of 150 new cDNA clones from brain which code for large proteins in vitro". DNA Research. 7 (1): 65–73. doi:10.1093/dnares/7.1.65. PMID10718198.
↑ 6.06.1Guillemot L, Citi S (2006). "Cingulin, a Cytoskeleton-Associated Protein of the Tight Junction". In Gonzalez-Mariscal L. Tight junctions. Georgetown, Texas: Landes Bioscience/Eurekah.com. pp. 54–63. ISBN978-0-387-36673-9.
↑Cordenonsi M, Turco F, D'atri F, Hammar E, Martinucci G, Meggio F, Citi S (September 1999). "Xenopus laevis occludin. Identification of in vitro phosphorylation sites by protein kinase CK2 and association with cingulin". European Journal of Biochemistry. 264 (2): 374–84. doi:10.1046/j.1432-1327.1999.00616.x. PMID10491082.
↑ 11.011.1Citi S, Paschoud S, Pulimeno P, Timolati F, De Robertis F, Jond L, Guillemot L (May 2009). "The tight junction protein cingulin regulates gene expression and RhoA signaling". Annals of the New York Academy of Sciences. 1165: 88–98. doi:10.1111/j.1749-6632.2009.04053.x. PMID19538293.
↑ 13.013.1Aijaz S, D'Atri F, Citi S, Balda MS, Matter K (May 2005). "Binding of GEF-H1 to the tight junction-associated adaptor cingulin results in inhibition of Rho signaling and G1/S phase transition". Developmental Cell. 8 (5): 777–86. doi:10.1016/j.devcel.2005.03.003. PMID15866167.
↑ 15.015.115.2Guillemot L, Schneider Y, Brun P, Castagliuolo I, Pizzuti D, Martines D, Jond L, Bongiovanni M, Citi S (November 2012). "Cingulin is dispensable for epithelial barrier function and tight junction structure, and plays a role in the control of claudin-2 expression and response to duodenal mucosa injury". Journal of Cell Science. 125 (Pt 21): 5005–14. doi:10.1242/jcs.101261. PMID22946046.
↑Kos R, Reedy MV, Johnson RL, Erickson CA (April 2001). "The winged-helix transcription factor FoxD3 is important for establishing the neural crest lineage and repressing melanogenesis in avian embryos". Development. 128 (8): 1467–79. PMID11262245.
↑Javed Q, Fleming TP, Hay M, Citi S (March 1993). "Tight junction protein cingulin is expressed by maternal and embryonic genomes during early mouse development". Development. 117 (3): 1145–51. PMID8325239.
↑Fleming TP, Hay M, Javed Q, Citi S (March 1993). "Localisation of tight junction protein cingulin is temporally and spatially regulated during early mouse development". Development. 117 (3): 1135–44. PMID8325238.
↑Cardellini P, Davanzo G, Citi S (September 1996). "Tight junctions in early amphibian development: detection of junctional cingulin from the 2-cell stage and its localization at the boundary of distinct membrane domains in dividing blastomeres in low calcium". Developmental Dynamics. 207 (1): 104–13. doi:10.1002/(SICI)1097-0177(199609)207:1<104::AID-AJA10>3.0.CO;2-0. PMID8875080.
↑Fesenko I, Kurth T, Sheth B, Fleming TP, Citi S, Hausen P (August 2000). "Tight junction biogenesis in the early Xenopus embryo". Mechanisms of Development. 96 (1): 51–65. doi:10.1016/s0925-4773(00)00368-3. PMID10940624.
↑Paschoud S, Bongiovanni M, Pache JC, Citi S (September 2007). "Claudin-1 and claudin-5 expression patterns differentiate lung squamous cell carcinomas from adenocarcinomas". Modern Pathology. 20 (9): 947–54. doi:10.1038/modpathol.3800835. PMID17585317.
↑Bordin M, D'Atri F, Guillemot L, Citi S (December 2004). "Histone deacetylase inhibitors up-regulate the expression of tight junction proteins". Molecular Cancer Research. 2 (12): 692–701. PMID15634758.
Further reading
Wolburg H, Lippoldt A (June 2002). "Tight junctions of the blood-brain barrier: development, composition and regulation". Vascular Pharmacology. 38 (6): 323–37. doi:10.1016/S1537-1891(02)00200-8. PMID12529927.
Bazzoni G, Martinez-Estrada OM, Orsenigo F, Cordenonsi M, Citi S, Dejana E (July 2000). "Interaction of junctional adhesion molecule with the tight junction components ZO-1, cingulin, and occludin". The Journal of Biological Chemistry. 275 (27): 20520–6. doi:10.1074/jbc.M905251199. PMID10877843.
D'Atri F, Nadalutti F, Citi S (August 2002). "Evidence for a functional interaction between cingulin and ZO-1 in cultured cells". The Journal of Biological Chemistry. 277 (31): 27757–64. doi:10.1074/jbc.M203717200. PMID12023291.
Gevaert K, Goethals M, Martens L, Van Damme J, Staes A, Thomas GR, Vandekerckhove J (May 2003). "Exploring proteomes and analyzing protein processing by mass spectrometric identification of sorted N-terminal peptides". Nature Biotechnology. 21 (5): 566–9. doi:10.1038/nbt810. PMID12665801.
Jin J, Smith FD, Stark C, Wells CD, Fawcett JP, Kulkarni S, Metalnikov P, O'Donnell P, Taylor P, Taylor L, Zougman A, Woodgett JR, Langeberg LK, Scott JD, Pawson T (August 2004). "Proteomic, functional, and domain-based analysis of in vivo 14-3-3 binding proteins involved in cytoskeletal regulation and cellular organization". Current Biology. 14 (16): 1436–50. doi:10.1016/j.cub.2004.07.051. PMID15324660.
Benzinger A, Muster N, Koch HB, Yates JR, Hermeking H (June 2005). "Targeted proteomic analysis of 14-3-3 sigma, a p53 effector commonly silenced in cancer". Molecular & Cellular Proteomics. 4 (6): 785–95. doi:10.1074/mcp.M500021-MCP200. PMID15778465.
Aijaz S, D'Atri F, Citi S, Balda MS, Matter K (May 2005). "Binding of GEF-H1 to the tight junction-associated adaptor cingulin results in inhibition of Rho signaling and G1/S phase transition". Developmental Cell. 8 (5): 777–86. doi:10.1016/j.devcel.2005.03.003. PMID15866167.
Kim JE, Tannenbaum SR, White FM (2005). "Global phosphoproteome of HT-29 human colon adenocarcinoma cells". Journal of Proteome Research. 4 (4): 1339–46. doi:10.1021/pr050048h. PMID16083285.