The Claudins family: Structure and function in normal and pathologic conditions

 

Abderrahman Ouban 1, Atif Ali Ahmed 2

1 Department of Pathology, College of Medicine, Prince Salman University, Kharj, Kingdom of Saudi Arabia, ouban@hotmail.com
2 Department of Pathology, Children's Mercy Hospital, University of Kansas, Kansas City, Missouri, USA, aahmed@cmh.edu

 

July 2012

 

 

Definition and introduction

Tight junctions (TJs) are the structures responsible for forming the seal that controls paracellular transport. TJs are composed of multiple components, including the Occludin proteins, the Zona Occludin proteins and the claudin proteins. The tertraspan integral membrane proteins known as claudins are essential for TJ formation and function (Tsukita and Furuse, 2000). Twenty three claudin genes are found in the human genome. The exact mechanisms of claudin evolution remain unknown, although some data suggest that the claudin multigene family evolved through gene duplications early in chordate development (Kollmar et al., 2001). In general, claudin genes are small, with few introns, or none at all (Lal-Nag and Morin, 2009). There is high degree of genetic homology among claudin genes, with several pairs showing similarity to each other in sequence and in intron/exon arrangement. Many claudin genes are closely located in the human genome, such as claudin 6 and claudin 9 on chromosome 16, claudin 22 and claudin 24 on chromosome 4, claudin 8 and claudin 17 on chromosome 21 and claudin 3 and claudin 4 on chromosome 7 (table 1). There is evidence that this genomic arrangement may result in coordinated expression as evidenced in co-expression of claudins 3 and 4 which has been reported in several normal and neoplastic tissues (Lal-Nag and Morin, 2009).

Claudin member Gene location (chromosomal regions) Protein size (amino acids) Protein size (Daltons)
1 3q28 221 22744
2 Xq22.3 230 24549
3 Xq11.23 220 23319
4 7q11 209 22077
5 22q11.21 218 23147
6 16p13.3 220 23292
7 17p13.3 221 22418
8 21q22.11 225 24845
9 16p13.3 217 22848

Table 1: Comparison of common claudins' gene locations and protein sizes.

Translation of the aforementioned genes results in 23 distinct human claudin proteins. These claudin proteins span the cellular membrane bilayer four times, where the N- and C-termini are oriented towards the cytoplasm and there are two extracellular loop domains (Morita et al., 1999). The C-Terminal PDZ binding motifs in each claudin binds other tight junction cytoplasmic proteins such as ZO-1, ZO-2, and ZO-3, MUPP-1, PALS-1 associated TJ protein (PATJ). Stabilization of a tight junction is specifically dependent on interaction of claudins with cytoplasmic scaffolding proteins ZO-1 and ZO-2 which link claudins to actin cytoskeleton (Umeda et al., 2006).
The TJ sealing strength varies over five orders of magnitude in different epithelia, from leaky proximal tubules to almost hermetic colon and urinary bladder. Tightness can also change in the same epithelium according to physiological and pathological conditions, in response to pharmacological changes and growth factors and hormonal stimulation (Balda et al., 1991). EGF plays a pivotal role in the adjustment of the permeability of TJs to physiological requirements, pathological conditions, and pharmacological interventions (Flores-Benítez et al., 2007).

 

Role of claudins in tumorigenesis, tumor progression and metastases

Recent gene and protein expression profiling analyses have shown that claudins' expression is frequently altered in several cancers (Swisshelm et al., 2005; Hewitt et al., 2006; Ouban and Ahmed, 2010; Ouban et al., 2012).
While the exact functions of claudins in cancer cells are not fully understood, recent work strongly suggests that claudins are involved in survival and invasion of tumor cells (Agarwal et al., 2005; Morin, 2005; Dhawan et al., 2005; Kominsky, 2006; Oku et al., 2006; Dos Reis et al., 2008).
Several studies on cancers have revealed down-regulation of claudins' expression including claudin-1 in breast cancer (Krämer et al., 2000) and claudin 7 in invasive breast cancer and in head and neck cancer (Al Moustafa et al., 2002; Kominsky et al., 2003). It is logical to expect this downregulation of claudins, because tumorigenesis is accompanied by disruption of tight junctions, with resultant loss of cohesion, invasiveness and lack of normal process of differentiation. However, it is interesting to note that numerous other studies have shown upregulation of these proteins in other cancers including, for example, claudins 3 and 4 over-expression in ovarian, breast, and prostate cancers (Long et al., 2001; Kominsky et al., 2003; Rangel et al., 2003), claudin 1 in oral squamous cell carcinomas (Dos Reis et al., 2008; Oku et al., 2006; Ouban et al., 2011). The over-expression of claudins in these cancers, which typically lose their TJs, is unexpected but probably related to roles unrelated to TJ formation (Hewitt et al., 2006). It is known that in addition to their function as a seal controlling the paracellular transport, tight junctions also play critical roles in maintaining cell polarity and signal transductions (Tsukita and Furuse, 2000; Van Itallie et al., 2006). It is through these functions that an over-expressed claudin protein may get involved in carcinogenesis and/or metastases. For example, claudins are important regulators of signal transduction from the cell-cell contact region (Gonzalez-Mariscal and Nava, 2005) and have also been shown to be directly recruiting and enhancing the activation of pro-matrix metalloproteinase 2 (MMP2) (Miyamori et al., 2001). MMP2 over-expression suggests a potential risk for invasion and metastasis in high-grade squamous intraepithelial lesions (Nasr et al., 2005) and pro-MMP2 activation is involved in pancreatic cancer progression (Ellenrieder et al., 2000).
CLDN1 has also been shown to be involved in the beta-catenin-Tcf/LEF signaling pathway and its over-expression was suggested to have a role in colorectal carcinogenesis (Miwa et al., 2000). The epidermal growth factor receptor (EGFR), has been suggested to regulate claudin proteins. EGF-induced EGFR activation increased CLDN1 expression in Madin-Darby canine kidney cells (Singh and Harris, 2004). EGFR is frequently amplified and over-expressed in many cancers, such as brain tumors (Schwechheimer et al., 1995), hepatocellular carcinomas (Tang et al., 1998), and head and neck carcinoma (Xia et al., 1999; Garnis et al., 2004); and increased expression of EGFR protein has been associated with worse prognosis (Bankfalvi et al., 2002).
The function of claudins in cancer is complex and diverse, with both over- and under-expression being linked to tumorigenesis. While the exact mechanism through which a claudin protein may predispose to carcinogenesis and metastases is still not clear in all cases, it is important to note the involvement of claudins in activation/recruitement of collagenases, activation of molecular neoplastic pathways such as the Wnt/Beta-catenin-TCF/LEF pathways, or with a growth factor well-known for its involvement in many tumor formations (EGF). Furthermore, the deregulated claudin protein may in fact result in further weakness of the tight junction of epithelial cells, resulting in porous gaps with influx of growth factors, hormones and toxins through paracellular spaces providing a habitable environment for tumor cells (Amasheh et al., 2002).
And while much work is in progress on this matter, it is important to note that claudin proteins expression may have significant clinical relevance (Morin, 2005; Swisshelm et al., 2005). For example claudin 10 expression in hepatocellular carcinoma (Cheung et al., 2005), claudin 1 expression in colorectal carcinoma (Dhawan et al., 2005), and claudin 1 expression in oral squamous cell carcinoma (Oku et al., 2006; Dos Reis et al., 2008) have all shown values in predicting behavior of tumor and prognosis for the patient.

 

 

Figure 1. Immunohistochemical detection of claudin-1 in squamous cell carcinoma of the esophagus.

 

 

Conclusions

Claudins show variable expression patterns in different types of epithelial malignancies. This fact provides a platform for anti-cancer therapeutic research trials that target claudins molecules or TJs in general. However the ubiquitous presence of claudins in normal and hyperplastic tissues in addition to neoplastic tissues may limit the usefulness of any future anti-claudin therapy. Immunohistochemical detection of some claudins has also proved useful as a diagnostic tool that can differentiate between various types of malignancies.
Certain claudins can also be used as markers that can predict patient's prognosis. Loss of claudins expression is also noted in several cancers and is related to metastasis in some cases. Thus it seems that identifying expression of claudins in various cancers is becoming increasingly useful in confirming the diagnosis, excluding other entities and judging patient's prognosis. Immunohistochemical detection of claudins will soon become part of the routine pathologic work-up of patients with various malignancies.

Bibliography

Assembly and sealing of tight junctions: possible participation of G-proteins, phospholipase C, protein kinase C and calmodulin.
Balda MS, Gonzalez-Mariscal L, Contreras RG, Macias-Silva M, Torres-Marquez ME, Garcia-Sainz JA, Cereijido M.
J Membr Biol. 1991 Jun;122(3):193-202.
PMID 1920385
 
EGFR gene amplification--rearrangement in human glioblastomas.
Schwechheimer K, Huang S, Cavenee WK.
Int J Cancer. 1995 Jul 17;62(2):145-8.
PMID 7622287
 
Alterations of oncogenes, tumor suppressor genes and growth factors in hepatocellular carcinoma: with relation to tumor size and invasiveness.
Tang Z, Qin L, Wang X, Zhou G, Liao Y, Weng Y, Jiang X, Lin Z, Liu K, Ye S.
Chin Med J (Engl). 1998 Apr;111(4):313-8.
PMID 10374394
 
Claudin multigene family encoding four-transmembrane domain protein components of tight junction strands.
Morita K, Furuse M, Fujimoto K, Tsukita S.
Proc Natl Acad Sci U S A. 1999 Jan 19;96(2):511-6.
PMID 9892664
 
Combination of EGFR, HER-2/neu, and HER-3 is a stronger predictor for the outcome of oral squamous cell carcinoma than any individual family members.
Xia W, Lau YK, Zhang HZ, Xiao FY, Johnston DA, Liu AR, Li L, Katz RL, Hung MC.
Clin Cancer Res. 1999 Dec;5(12):4164-74.
PMID 10632356
 
Role of MT-MMPs and MMP-2 in pancreatic cancer progression.
Ellenrieder V, Alber B, Lacher U, Hendler SF, Menke A, Boeck W, Wagner M, Wilda M, Friess H, Buchler M, Adler G, Gress TM.
Int J Cancer. 2000 Jan 1;85(1):14-20.
PMID 10585576
 
Genomic organization of claudin-1 and its assessment in hereditary and sporadic breast cancer.
Kramer F, White K, Kubbies M, Swisshelm K, Weber BH.
Hum Genet. 2000 Sep;107(3):249-56.
PMID 11071387
 
Pores in the wall: claudins constitute tight junction strands containing aqueous pores.
Tsukita S, Furuse M.
J Cell Biol. 2000 Apr 3;149(1):13-6.
PMID 10747082
 
Expression and phylogeny of claudins in vertebrate primordia.
Kollmar R, Nakamura SK, Kappler JA, Hudspeth AJ.
Proc Natl Acad Sci U S A. 2001 Aug 28;98(18):10196-201. Epub 2001 Aug 21.
PMID 11517306
 
Expression of Clostridium perfringens enterotoxin receptors claudin-3 and claudin-4 in prostate cancer epithelium.
Long H, Crean CD, Lee WH, Cummings OW, Gabig TG.
Cancer Res. 2001 Nov 1;61(21):7878-81.
PMID 11691807
 
Involvement of claudin-1 in the beta-catenin/Tcf signaling pathway and its frequent upregulation in human colorectal cancers.
Miwa N, Furuse M, Tsukita S, Niikawa N, Nakamura Y, Furukawa Y.
Oncol Res. 2001;12(11-12):469-76.
PMID 11939410
 
Claudin promotes activation of pro-matrix metalloproteinase-2 mediated by membrane-type matrix metalloproteinases.
Miyamori H, Takino T, Kobayashi Y, Tokai H, Itoh Y, Seiki M, Sato H.
J Biol Chem. 2001 Jul 27;276(30):28204-11. Epub 2001 May 29.
PMID 11382769
 
Identification of genes associated with head and neck carcinogenesis by cDNA microarray comparison between matched primary normal epithelial and squamous carcinoma cells.
Al Moustafa AE, Alaoui-Jamali MA, Batist G, Hernandez-Perez M, Serruya C, Alpert L, Black MJ, Sladek R, Foulkes WD.
Oncogene. 2002 Apr 18;21(17):2634-40.
PMID 11965536
 
Claudin-2 expression induces cation-selective channels in tight junctions of epithelial cells.
Amasheh S, Meiri N, Gitter AH, Schoneberg T, Mankertz J, Schulzke JD, Fromm M.
J Cell Sci. 2002 Dec 15;115(Pt 24):4969-76.
PMID 12432083
 
Deranged expression of the E-cadherin/beta-catenin complex and the epidermal growth factor receptor in the clinical evolution and progression of oral squamous cell carcinomas.
Bankfalvi A, Krassort M, Vegh A, Felszeghy E, Piffko J.
J Oral Pathol Med. 2002 Sep;31(8):450-7.
PMID 12220351
 
Loss of the tight junction protein claudin-7 correlates with histological grade in both ductal carcinoma in situ and invasive ductal carcinoma of the breast.
Kominsky SL, Argani P, Korz D, Evron E, Raman V, Garrett E, Rein A, Sauter G, Kallioniemi OP, Sukumar S.
Oncogene. 2003 Apr 3;22(13):2021-33.
PMID 12673207
 
Tight junction proteins claudin-3 and claudin-4 are frequently overexpressed in ovarian cancer but not in ovarian cystadenomas.
Rangel LB, Agarwal R, D'Souza T, Pizer ES, Alo PL, Lancaster WD, Gregoire L, Schwartz DR, Cho KR, Morin PJ.
Clin Cancer Res. 2003 Jul;9(7):2567-75.
PMID 12855632
 
OCGR array: an oral cancer genomic regional array for comparative genomic hybridization analysis.
Garnis C, Campbell J, Zhang L, Rosin MP, Lam WL.
Oral Oncol. 2004 May;40(5):511-9.
PMID 15006624
 
Epidermal growth factor receptor activation differentially regulates claudin expression and enhances transepithelial resistance in Madin-Darby canine kidney cells.
Singh AB, Harris RC.
J Biol Chem. 2004 Jan 30;279(5):3543-52. Epub 2003 Oct 30.
PMID 14593119
 
Claudin-3 and claudin-4 expression in ovarian epithelial cells enhances invasion and is associated with increased matrix metalloproteinase-2 activity.
Agarwal R, D'Souza T, Morin PJ.
Cancer Res. 2005 Aug 15;65(16):7378-85.
PMID 16103090
 
Claudin-10 expression level is associated with recurrence of primary hepatocellular carcinoma.
Cheung ST, Leung KL, Ip YC, Chen X, Fong DY, Ng IO, Fan ST, So S.
Clin Cancer Res. 2005 Jan 15;11(2 Pt 1):551-6.
PMID 15701840
 
Claudin-1 regulates cellular transformation and metastatic behavior in colon cancer.
Dhawan P, Singh AB, Deane NG, No Y, Shiou SR, Schmidt C, Neff J, Washington MK, Beauchamp RD.
J Clin Invest. 2005 Jul;115(7):1765-76. Epub 2005 Jun 16.
PMID 15965503
 
Tight junctions, from tight intercellular seals to sophisticated protein complexes involved in drug delivery, pathogens interaction and cell proliferation.
Gonzalez-Mariscal L, Nava P.
Adv Drug Deliv Rev. 2005 Apr 25;57(6):811-4.
PMID 15820554
 
Claudin proteins in human cancer: promising new targets for diagnosis and therapy.
Morin PJ.
Cancer Res. 2005 Nov 1;65(21):9603-6.
PMID 16266975
 
Expression of matrix metalloproteinase-2 in preinvasive and invasive carcinoma of the uterine cervix.
Nasr M, Ayyad SB, El-Lamie IK, Mikhail MY.
Eur J Gynaecol Oncol. 2005;26(2):199-202.
PMID 15857029
 
Role of claudins in tumorigenesis.
Swisshelm K, Macek R, Kubbies M.
Adv Drug Deliv Rev. 2005 Apr 25;57(6):919-28.
PMID 15820559
 
The claudin gene family: expression in normal and neoplastic tissues.
Hewitt KJ, Agarwal R, Morin PJ.
BMC Cancer. 2006 Jul 12;6:186.
PMID 16836752
 
Claudins: emerging targets for cancer therapy.
Kominsky SL.
Expert Rev Mol Med. 2006 Aug 4;8(18):1-11.
PMID 16887048
 
Tight junction protein claudin-1 enhances the invasive activity of oral squamous cell carcinoma cells by promoting cleavage of laminin-5 gamma2 chain via matrix metalloproteinase (MMP)-2 and membrane-type MMP-1.
Oku N, Sasabe E, Ueta E, Yamamoto T, Osaki T.
Cancer Res. 2006 May 15;66(10):5251-7.
PMID 16707450
 
ZO-1 and ZO-2 independently determine where claudins are polymerized in tight-junction strand formation.
Umeda K, Ikenouchi J, Katahira-Tayama S, Furuse K, Sasaki H, Nakayama M, Matsui T, Tsukita S, Furuse M, Tsukita S.
Cell. 2006 Aug 25;126(4):741-54.
PMID 16923393
 
Two splice variants of claudin-10 in the kidney create paracellular pores with different ion selectivities.
Van Itallie CM, Rogan S, Yu A, Vidal LS, Holmes J, Anderson JM.
Am J Physiol Renal Physiol. 2006 Dec;291(6):F1288-99. Epub 2006 Jun 27.
PMID 16804102
 
Control of tight junctional sealing: role of epidermal growth factor.
Flores-Benitez D, Ruiz-Cabrera A, Flores-Maldonado C, Shoshani L, Cereijido M, Contreras RG.
Am J Physiol Renal Physiol. 2007 Feb;292(2):F828-36. Epub 2006 Oct 31.
PMID 17077385
 
Claudin 1 overexpression increases invasion and is associated with aggressive histological features in oral squamous cell carcinoma.
Dos Reis PP, Bharadwaj RR, Machado J, Macmillan C, Pintilie M, Sukhai MA, Perez-Ordonez B, Gullane P, Irish J, Kamel-Reid S.
Cancer. 2008 Dec 1;113(11):3169-80.
PMID 18991282
 
Regulation and roles for claudin-family tight junction proteins.
Findley MK, Koval M.
IUBMB Life. 2009 Apr;61(4):431-7.
PMID 19319969
 
The claudins.
Lal-Nag M, Morin PJ.
Genome Biol. 2009;10(8):235. Epub 2009 Aug 26.
PMID 19706201
 
Claudins in human cancer: a review.
Ouban A, Ahmed AA.
Histol Histopathol. 2010 Jan;25(1):83-90.
PMID 19924644
 
Claudin-1 expression in squamous cell carcinomas of different organs: comparative study of cancerous tissues and normal controls.
Ouban A, Hamdan H, Hakam A, Ahmed AA.
Int J Surg Pathol. 2012 Apr;20(2):132-8. Epub 2011 Oct 13.
PMID 21997594
 
Written2012-07Abderrahman Ouban, Atif Ali Ahmed
of Pathology, College of Medicine, Prince Salman University, Kharj, Kingdom of Saudi Arabia (AO); Department of Pathology, Children's Mercy Hospital, University of Kansas, Kansas City, Missouri, USA (AAA)

Citation

This paper should be referenced as such :
Ouban, A ; Ahmed, AA
The Claudins family: Structure, function in normal, pathologic conditions
Atlas Genet Cytogenet Oncol Haematol. 2012;16(12):943-947.
Free journal version : [ pdf ]   [ DOI ]
On line version : http://AtlasGeneticsOncology.org/Deep/ClaudinFamID20113.htm

Citation

Atlas of Genetics and Cytogenetics in Oncology and Haematology

The Claudins family: Structure and function in normal and pathologic conditions

Online version: http://atlasgeneticsoncology.org/deep-insight/20113/the-claudins-family-structure-and-function-in-normal-and-pathologic-conditions