TY - JOUR
T1 - Cx32 formation and/or Cx32-mediated intercellular communication induces expression and function of tight junctions in hepatocytic cell line
AU - Kojima, Takashi
AU - Spray, David C.
AU - Kokai, Yasuo
AU - Chiba, Hideki
AU - Mochizuki, Yohichi
AU - Sawada, Norimasa
N1 - Funding Information:
We are grateful to Dr. S. M. Deschenes (University of Pennsylvania Medical Center, PA) for mutant Cx32 cDNA (R220Stop). We thank Ms. M. Urban (Albert Einstein College of Medicine, New York) for technical support. This work was supported in part by grants-in-aid from the Ministry of Education, Culture, Sports and Science, and the Ministry of Welfare of Japan, by the Smoking Research Funda-tion, and by NIH PO1 (DK41918).
PY - 2002
Y1 - 2002
N2 - Gap junctional intercellular communication (GJIC) is thought to play a crucial role in cell differentiation. Small gap junction plaques are frequently associated with tight junction strands in hepatocytes, suggesting that gap junctions may be closely related to the role of tight junctions in the establishment of cell polarity. To examine the exact role of gap junctions in regulating tight junctions, we transfected connexin 32 (Cx32), Cx26, or Cx43 cDNAs into immortalized mouse hepatocytes derived from Cx32-deficient mice and examined the expression and function of the endogenous tight junction molecules. In transient wild-type Cx32 transfectants, immunocytochemistry revealed that endogenous occludin was in part localized at cell borders, where it was colocalized with Cx32, whereas neither was detected in parental cells. In Cx32 null hepatocytes transfected with Cx32 truncated at position 220 (R220stop), wild-type Cx26, or wild-type Cx43 cDNAs, occludin was not detected at cell borders. In stable wild-type Cx32 transfectants, occludin, claudin-1, and ZO-1 mRNAs and proteins were significantly increased compared to parental cells and all of the proteins were colocalized with Cx32 at cell borders. Treatment with a GJIC blocker, 18β-glycyrrhetinic acid, resulted in decreases of occludin and claudin-1 at cell borders in the stable transfectants. The induction of tight junction proteins in the stable transfectants was accompanied by an increase in both fence and barrier functions of tight junctions. Furthermore, in the stable transfectants, circumferencial actin filaments were also increased without a change of actin protein. These results indicate that Cx32 formation and/or Cx32-mediated intercellular communication may participate in the formation of functional tight junctions and actin organization.
AB - Gap junctional intercellular communication (GJIC) is thought to play a crucial role in cell differentiation. Small gap junction plaques are frequently associated with tight junction strands in hepatocytes, suggesting that gap junctions may be closely related to the role of tight junctions in the establishment of cell polarity. To examine the exact role of gap junctions in regulating tight junctions, we transfected connexin 32 (Cx32), Cx26, or Cx43 cDNAs into immortalized mouse hepatocytes derived from Cx32-deficient mice and examined the expression and function of the endogenous tight junction molecules. In transient wild-type Cx32 transfectants, immunocytochemistry revealed that endogenous occludin was in part localized at cell borders, where it was colocalized with Cx32, whereas neither was detected in parental cells. In Cx32 null hepatocytes transfected with Cx32 truncated at position 220 (R220stop), wild-type Cx26, or wild-type Cx43 cDNAs, occludin was not detected at cell borders. In stable wild-type Cx32 transfectants, occludin, claudin-1, and ZO-1 mRNAs and proteins were significantly increased compared to parental cells and all of the proteins were colocalized with Cx32 at cell borders. Treatment with a GJIC blocker, 18β-glycyrrhetinic acid, resulted in decreases of occludin and claudin-1 at cell borders in the stable transfectants. The induction of tight junction proteins in the stable transfectants was accompanied by an increase in both fence and barrier functions of tight junctions. Furthermore, in the stable transfectants, circumferencial actin filaments were also increased without a change of actin protein. These results indicate that Cx32 formation and/or Cx32-mediated intercellular communication may participate in the formation of functional tight junctions and actin organization.
KW - Actin
KW - Claudin-1
KW - Gap junctions
KW - Occludin
KW - ZO-1
UR - http://www.scopus.com/inward/record.url?scp=0036343899&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0036343899&partnerID=8YFLogxK
U2 - 10.1006/excr.2002.5511
DO - 10.1006/excr.2002.5511
M3 - Article
C2 - 11978007
AN - SCOPUS:0036343899
SN - 0014-4827
VL - 276
SP - 40
EP - 51
JO - Experimental Cell Research
JF - Experimental Cell Research
IS - 1
ER -