Maintenance of cell junctions plays a crucial role in the regulation of cellular functions including cell proliferation, permeability, and cell death. Disruption of cell junctions is implicated in a variety of human disorders, such as inflammatory diseases and cancers. Understanding molecular regulation of cell junctions is important for development of therapeutic strategies for intervention of human diseases. Ubiquitination is an important type of post-translational modification that primarily regulates endogenous protein stability, receptor internalization, enzyme activity, and protein-protein interactions. Ubiquitination is tightly regulated by ubiquitin E3 ligases and can be reversed by deubiquitinating enzymes. Recent studies have been focusing on investigating the effect of protein stability in the regulation of cell-cell junctions. Ubiquitination and degradation of cadherins, claudins, and their interacting proteins are implicated in epithelial and endothelial barrier disruption. Recent studies have revealed that ubiquitination is involved in regulation of Rho GTPases' biological activities. Taken together these studies, ubiquitination plays a critical role in modulating cell junctions and motility. In this review, we will discuss the effects of ubiquitination and deubiquitination on protein stability and expression of key proteins in the cell-cell junctions, including junction proteins, their interacting proteins, and small Rho GTPases. We provide an overview of protein stability in modulation of epithelial and endothelial barrier integrity and introduce potential future search directions to better understand the effects of ubiquitination on human disorders caused by dysfunction of cell junctions.
Animals ; Humans ; Inflammation ; metabolism ; pathology ; Intercellular Junctions ; metabolism ; Neoplasms ; metabolism ; pathology ; Protein Stability ; Ubiquitin-Protein Ligases ; metabolism ; Ubiquitination

OBJECTIVETo inhibit the expression of connexin43 (Cx43) in the human corpus cavernosum penis smooth muscle cells by small interfering RNA (siRNA) and detect the gap junction intercellular communication (GJIC), and to investigate the application of siRNA technology in the gap junction of corpus cavernosum penis smooth muscle cells and its role in the penile erection process.

METHODSWith the help of the software of Ambion Corporation, the specific recombinant plasmids with siRNA targeting human Cx43 gene were constructed. The recombinant plasmids having been stably transferred into human corpus cavernosum penis smooth muscle cells for 48 hours, semi-quantitive reverse transcription polymerase chain reaction (RT-PCR) and Western blotting techniques were used to examine the inhibitory effects of siRNA on the expressions of the Cx43 gene and protein, in comparison with the siRNA negative control and the blank control group, respectively. The GJIC was detected by scrape-loading and fluorescence dye transfer experiments through the fluorescence microscope.

RESULTSThe results of enzyme digestion analysis and DNA sequencing showed that the recombinant plasmid pSilencer 1.0-U6-siRNA-Cx43 was successfully constructed. The relative levels of Cx43 mRNA and protein expression in the smooth muscle cells were (0.45 +/- 0.08)% and (0.56 +/- 0.06)% after successful transfer of the recombinant plasmid. However, the expression levels of mRNA and protein were (0.72 +/- 0.04)% and (0.80 +/- 0.08)% in the negative siRNA transfer group, and (0.74 +/- 0.09)% and (0.77 +/- 0.11)% in the blank control, respectively, with a significant difference (P < 0.05). The GJIC also decreased significantly.

CONCLUSIONsiRNA can significantly inhibit the expression of Cx43 and block the GJIC in the human corpus cavernosum penis smooth muscle cells. siRNA technology plays an important role in penile erection and flaccidity.

Blotting, Northern ; Cells, Cultured ; Connexin 43 ; biosynthesis ; genetics ; Humans ; Intercellular Junctions ; Male ; Myocytes, Smooth Muscle ; physiology ; Penis ; cytology ; metabolism ; RNA, Small Interfering ; Reverse Transcriptase Polymerase Chain Reaction ; Transfection

OBJECTIVETo explore the molecular mechanism of dutasteride inhibiting fertility by studying its effects on the expressions of the epididymal epithelial junction proteins Claudin1 and β-catenin in rats.

METHODSSixteen 3-month-old SD male rats were equally divided into an experimental and a negative control group to be treated intragastrically with dutasteride at 40 mg/kg per day and the same dose of solvent, respectively, for 14 consecutive days. Then, the sperm motility and morphology of the rats were detected by computer-assisted sperm analysis, the serum levels of testosterone (T) and dihydrotestosterone (DHT) measured by ELISA, changes in the tight junction of epididymal cells observed under the transmission electron microscope, the protein and gene expressions of Claudin1 and β-catenin determined by RT-PCR and immunohistochemistry, and the conception rate of the mated female rats calculated.

RESULTSDutasteride significantly suppressed the serum DHT level, sperm motility, and fertility of the rats (P <0.05). Interspaces between epididymal epithelial cell tight junctions were observed, the volume of epididymal fluid obviously increased, and the expressions of Claudin1 and β-catenin gene and protein remarkably downregulated in the experimental rats (P <0.05).

CONCLUSIONDutasteride can significantly inhibit the fertility of male rats by reducing the serum DHT level, suppressing Claudin1 and β-catenin expressions, and damaging epididymal epithelial cell junctions.

Animals ; Azasteroids ; pharmacology ; Claudin-1 ; metabolism ; Dihydrotestosterone ; blood ; Dutasteride ; Epididymis ; drug effects ; metabolism ; Female ; Fertility ; drug effects ; Humans ; Intercellular Junctions ; drug effects ; Male ; Rats ; Rats, Sprague-Dawley ; Sperm Motility ; drug effects ; Testosterone ; blood ; Urological Agents ; pharmacology ; beta Catenin ; metabolism

Men with diabetic erectile dysfunction (ED) respond poorly to the currently available oral phosphodiesterase-5 inhibitors. Therefore, functional therapies for diabetic ED are needed. Stromal vascular fraction (SVF) and the adenovirus-mediated cartilage oligomeric matrix angiopoietin-1 (Ad-COMP-Ang1) gene are known to play critical roles in penile erection. We previously reported that SVF and Ad-COMP-Ang1 have only a short-term effect in restoring erectile function. Further improvements to ED therapy are needed for long-lasting effects. In the present study, we aimed to test if the combination of SVF and Ad-COMP-Ang1 could extend the erection effect in diabetic ED. We found that the combination therapy showed a long-term effect in restoring erectile function through enhanced penile endothelial and neural cell regeneration. Combination therapy with SVF and Ad-COMP-Ang1 notably restored cavernous endothelial cell numbers, pericyte numbers, endothelial cell-cell junctions, decreased cavernous endothelial cell permeability, and promoted neural regeneration for at least 4 weeks in diabetic mice. In summary, this is an initial description of the long-term effect of combination therapy with SVF and Ad-COMP-Ang1 in restoring erectile function through a dual effect on endothelial and neural cell regeneration. Such combination therapy may have therapeutic potential for the treatment of diabetic ED.
Angiopoietin-1/genetics* ; Animals ; Diabetes Mellitus, Experimental/metabolism* ; Endothelium, Vascular/metabolism* ; Erectile Dysfunction/therapy* ; Genetic Therapy/methods* ; Intercellular Junctions/metabolism* ; Male ; Mesenchymal Stem Cell Transplantation ; Mice ; Penile Erection/physiology* ; Permeability

OBJECTIVETo study on the expression patterns of proteins associated with cell junctions in the developing mouse testes.

METHODThe expression levels of reproductive related cell lines spermatogonia cell line GC1 spg, spermatocyte cell line GC2 spg, leydig cell line TM3, and sertoli cell line TM4, primary sertoli cells, and 1-6-week mouse testes were analyzed using Western blot.

RESULTSThe sertoli cell junction-associated membrane proteins adhesion molecule A, Occludin and Claudin, and the sertoli-germ cell junction-associated membrane proteins junctional adhesion molecule C, Nectin-3, and E-cadherin were stage-specific in the seminiferous tubules in the mouse testes. The adaptor proteins associated with cell juctions zonula occludens-1, zonula occludens-2, Afadin, Β-catenin, and CD2-associated protein were not stage-specific in the seminiferous tubules in the mouse testes.

CONCLUSIONSIn the seminiferous tubules in the mouse testes, the membrane proteins associated with cell junctions are stage-specific. However, the expressions of adaptor proteins associated with cell junctions do not obviously change.

Adaptor Proteins, Signal Transducing ; metabolism ; Animals ; Cdh1 Proteins ; metabolism ; Cell Adhesion Molecules ; metabolism ; Cell Line ; Cytoskeletal Proteins ; metabolism ; Humans ; Intercellular Junctions ; metabolism ; Male ; Membrane Proteins ; metabolism ; Mice ; Microfilament Proteins ; metabolism ; Nectins ; Seminiferous Tubules ; cytology ; metabolism ; Sertoli Cells ; cytology ; Testis ; cytology ; Zonula Occludens-1 Protein ; metabolism ; Zonula Occludens-2 Protein ; metabolism ; beta Catenin ; metabolism

The integrity of blood vessels controls vascular permeability and extravasation of blood cells, across the endothelium. Thus, the impairment of endothelial integrity leads to hemorrhage, edema, and inflammatory infiltration. However, the molecular mechanism underlying vascular integrity has not been fully understood. Here, we demonstrate an essential role for A-kinase anchoring protein 12 (AKAP12) in the maintenance of endothelial integrity during vascular development. Zebrafish embryos depleted of akap12 (akap12 morphants) exhibited severe hemorrhages. In vivo time-lapse analyses suggested that disorganized interendothelial cell-cell adhesions in akap12 morphants might be the cause of hemorrhage. To clarify the molecular mechanism by which the cell-cell adhesions are impaired, we examined the cell-cell adhesion molecules and their regulators using cultured endothelial cells. The expression of PAK2, an actin cytoskeletal regulator, and AF6, a connector of intercellular adhesion molecules and actin cytoskeleton, was reduced in AKAP12-depleted cells. Depletion of either PAK2 or AF6 phenocopied AKAP12-depleted cells, suggesting the reduction of PAK2 and AF6 results in the loosening of intercellular junctions. Consistent with this, overexpression of PAK2 and AF6 rescued the abnormal hemorrhage in akap12 morphants. We conclude that AKAP12 is essential for integrity of endothelium by maintaining the expression of PAK2 and AF6 during vascular development.
A Kinase Anchor Proteins/*genetics/metabolism ; Animals ; Blood Vessels/abnormalities/*embryology/metabolism ; Cell Cycle Proteins/genetics/metabolism ; Down-Regulation ; Embryo, Nonmammalian/abnormalities/*blood supply/embryology/metabolism ; Gene Deletion ; *Gene Expression Regulation, Developmental ; Hemorrhage/*embryology/genetics/metabolism ; Human Umbilical Vein Endothelial Cells ; Humans ; Intercellular Junctions/genetics/metabolism/ultrastructure ; Kinesin/genetics/metabolism ; Myosins/genetics/metabolism ; Zebrafish/*embryology/genetics ; p21-Activated Kinases/genetics/metabolism

AIMTo understand the biological functions of the ectoplasmic specializations between Sertoli cells and maturing spermatids in seminiferous epithelia.

METHODSIn order to disrupt the function of the ectoplasmic specializations, nectin-2, which is expressed at the specialization, was neutralized with anti-nectin-2 antibody micro-injected into the lumen of the mouse seminiferous tubule. Anti-nectin-3 antibody was also micro-injected into the lumen in order to neutralize nectin-3, which is expressed at the specialization.

RESULTSThe actin filaments at the specialization disappeared, and exfoliation of maturing spermatids was observed by electron microscopy.

CONCLUSIONNectin-2 was neutralized by anti-nectin-2 antibody and nectin-3 was neutralized by anti-nectin-3 antibody, respectively. Inactivated nectin-2 and nectin-3 disrupted the nectin-afadin-actin system, and finally the actin filaments disappeared. As a result, the specialization lost the holding function and detachment of spermatids was observed. One of the functions of the specialization seems to be to hold maturing spermatids until spermiation.

Actins ; metabolism ; Animals ; Antibodies ; immunology ; pharmacology ; Cell Adhesion Molecules ; immunology ; metabolism ; Cell Communication ; drug effects ; physiology ; Intercellular Junctions ; drug effects ; metabolism ; Male ; Mice ; Mice, Inbred ICR ; Microfilament Proteins ; metabolism ; Microscopy, Confocal ; Nectins ; Seminiferous Epithelium ; cytology ; drug effects ; metabolism ; Sertoli Cells ; cytology ; drug effects ; metabolism ; Spermatids ; cytology ; drug effects ; metabolism

OBJECTIVETo investigate the antiproliferative and anti-metastasis effect of Xihuang Pill (, XP) on human colorectal cancer cell and to explore the molecular mechanism by which it produces the effects.

METHODSHighly metastatic human colorectal cancer cell line LoVo was treated with low-, medium-, and highdose XP-containing serum (XP-L, XP-M, XP-H) groups for 48 h, cells intervened with no drug rat serum and PD98059 [extracellular signal-regulated kinase (ERK) inhibitor] as negative and positive controls (NC and PC) groups. Cell proliferation assay was made using cell counting kit-8 (CCK8). The 8 μm pore-size transwell chamber and 4', 6-diamidino-2-phenylindole (DAPI) staining were applied to examine the ability of invasion and migration of the cells. The protein expression of ERK1/2, zinc fifi nger E-box-binding homeobox 1 (ZEB1), Scrib and lethal giant larvae homolog 2 (Lgl2) was detected by Western blotting while the relative mRNA quantity of E-cadherin, N-cadherin, Occludin and junctional adhesion molecule-1 (JAM1) was measured by realtime fluorescent quantitative polymerase chain reaction (RT-qPCR).

RESULTSXP induced a dose-dependent suppression on the proliferation of LoVo cells (P <0.05 or P<0.01), with the inhibition rates varied from 27.30% to 31.08%. Transwell assay showed that when preprocessed with PD98059 and XP-containing serum, the number of cells that passed the filter decreased significantly compared with that of NC group (P <0.05 or P<0.01). Moreover, XP inhibited the protein expression of ERK1/2 and ZEB1 (P <0.05); and up-regulated the protein expression of Scrib and Lgl2 (P <0.05). The mRNA levels of E-cadherin, Occludin and JAM1 of the XP intervened groups and PC group markedly ascended (P <0.05) while that of N-cadherin showed a descending tendency (P>0.05).

CONCLUSIONXP intervention suppressed the ability of proliferation, invasion and migration of the LoVo cells. Regulating ZEB1-SCRIB Loop so as to recover epithelial phenotype and apical junctional complex might be one of the mechanisms by which XP produces the anti-metastasis effect.

Animals ; Cadherins ; genetics ; metabolism ; Cell Line, Tumor ; Cell Movement ; drug effects ; Cell Polarity ; drug effects ; genetics ; Cell Proliferation ; drug effects ; Colorectal Neoplasms ; genetics ; pathology ; Drugs, Chinese Herbal ; pharmacology ; Epithelial-Mesenchymal Transition ; drug effects ; genetics ; Gene Expression Regulation, Neoplastic ; drug effects ; Homeodomain Proteins ; metabolism ; Humans ; Intercellular Junctions ; drug effects ; metabolism ; Membrane Proteins ; metabolism ; Neoplasm Invasiveness ; Phenotype ; RNA, Messenger ; genetics ; metabolism ; Rats, Wistar ; Transcription Factors ; metabolism ; Tumor Suppressor Proteins ; metabolism ; Zinc Finger E-box-Binding Homeobox 1