Caveolin and Focal Adhesion Proteins Talin and Paxillin During Early Pregnancy in the Rat and in Human Ishikawa Cells.

Adhesion to extracellular matrix is mediated primarily by integrins, which cluster with other proteins at focal adhesions. Caveolin has also been reported to be linked with integrins. At the time of implantation integrins β1 and β3 disassemble from basal focal adhesions with integrin β3 becoming apically localised in rat uterine epithelial cells and also in Ishikawa cells, a model cell line for a receptive endometrium. Paxillin and talin are two proteins that are essential components of the focal adhesion complex. Both paxillin and talin are lost basally in rat luminal epithelial cells at the time of implantation, indicating their importance in the loss of focal adhesions at this time. The present study investigated the localisation of caveolin 1 and 2 in rat uterine epithelial cells during early pregnancy, and also paxillin and talin in human Ishikawa cells, to determine their role in focal adhesion dynamics. Caveolin 1 and 2 in rat uterine epithelial cells during early pregnancy are cytoplasmic on day 1 and become increasingly basal at the time of implantation. At this time there is a statistically significant increase in caveolin 1 protein expression, while caveolin 2 is reduced. Ovariectomised rats treated with different hormonal regimes indicated that the basal localisation of caveolin 1 and 2 in luminal uterine epithelia is dependent on progesterone. Confocal immunofluorescence microscopy of Ishikawa cells grown on glass coverslips coated with matrigel showed that caveolins 1 and 2, talin and paxillin are localised apically in Ishikawa cells when provided with an extracellular matrix. This is in contrast to the absence of these proteins in Ishikawa cells when grown directly on glass. Hence it appears that the presence of an extracellular matrix is important for the expression of talin, paxillin and caveolin. Hormonal treatment of Ishikawa cells did not however alter the localisation of caveolins 1 and 2 or paxillin and talin. The present results suggest that at the time of implantation, caveolin in rat luminal uterine epithelial cells may have possible roles in trafficking of various proteins for either degradation or relocation such as those found in focal adhesions, namely talin, paxillin and potentially integrins, which may play a role during successful blastocyst implantation. This is supported by the observation that caveolin, talin and paxillin are apically localised in Ishikawa cells.(poster)