Cell kinetic status of mouse lens epithelial cells lacking αA- and αB-crystallin

αA- and αB-crystallins are small heat shock proteins and molecular chaperones that are known to prevent non-specific aggregation of denaturing proteins. Recent work indicates that α A-/- lens epithelial cells grow at a slower rate than wild-type cells, and cultured αB-/- cells demonstrate increased hyperproliferation and genomic instability, suggesting that these proteins may exert a direct effect on the cell cycle kinetics, and influence cell proliferation. However, the cell cycle parameters of αA/αBKO (double knockout) cells have not been analyzed. Here we investigate the cell cycle kinetics of synchronized mouse lens epithelial cultures derived from wild-type and αA/αB double knockout (αA/αBKO) mice using BrdU labeling of proliferating cells, and flow cytometric analysis. We also provide data on the changing pattern of expression of HSP25, a small heat shock protein in αA/αBKO and wild-type cells during the cell cycle. Using serum starvation to synchronize cells in the quiescent GO phase, and restimulation with serum followed by BrdU labeling and flow cytometry, the data indicated that as compared to wild-type cells, a <50% smaller fraction of the αA/αBKO cells entered the DNA synthetic S phase of the cell cycle. Furthermore, there was a delay in cell cycle transit through S phase in αA/αBKO cells, suggesting that although capable of entering S phase, the αA/αBKO cells are blocked in G1 phase, and are delayed in their cell cycle progression. Immunoblot analysis with antibodies to the small heat shock protein HSP25 indicated that although HSP25 increased in G1 phase of wild-type cells, and remained elevated on further progression through the cell cycle, HSP25 accumulation was delayed to S phase in αA/αBKO cells. These data can be interpreted to indicate that mouse lens epithelial cell progression through the cell cycle is significantly affected by expression of αA and αB-crystallin.