Decreased Expression of α3 and β1 Integrin Subunits is Responsible for Differentiation-Associated Changes in Cells Behavior in Terminally Differentiated Human Oral Keratinocytes

摘要

Primary normal human oral keratinocytes (NHOKs) terminally differentiate in serial subculture. To investigate whether this subculture-induced differentiation of NHOKs affects integrin expression and cell-matrix interaction, we studied the expression levels of integrin subunits and cellular response to the extracellular matrix (ECM) proteins in NHOKs at different population doublings. The phosphorylation statuses of focal adhesion kinase (FAK), extracellular signal regulated kinase (ERK), p38, and c-Jun amino-terminal kinase (JNK) were also determined in NH OK cells cultured on ECM proteins, to evaluate the functions of interns with respect to cellular responses to ECM proteins. The expression levels of α3 and β1 integrin subunits progressively decreased in NHOKs undergoing terminal differentiation. The ability of NHOKs to spread upon laminin and type I collagen significantly decreased in terminally differentiated oral keratinocytes. Keratinocyte migration was significantly increased on type I collagen for terminally differentiated NHOKs. Similar results were seen following preincubation of rapidly proliferating NHOKs with function-blocking antibodies to α3 or β1 integrin subunit. In contrast, fibronectin had no effect on cellular responses in NHOKs, which were almost negligible in the expression levels of α5 integrin subunits. The extent of FAK phosphorylation in terminally differentiated NHOKs was notably lower than that of rapidly proliferating cells, but was enhanced in terminally differentiated cells that were cultured on type I collagen. Our results indicate that decreased expression of α3 and β1 integrin subunits is responsible for differentiation-associated changes in cells behavior in terminally differentiated oral keratinocytes. Our data also show that the aborgation of the α5β1 integrin function caused by omitting α5 subunit is linked to the loss of a cell-fibronectin interaction in human oral keratinocytes.