aB-Crystallin Selectively Targets Intermediate Filament Proteins during Thermal Stress

RESULTS. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and western immunoblot analyses showed selective interactions in lens cell homogenates between MBP-aB and endogenous aAand aB-crystallins, the lens-specific intermediate filament proteins phakinin (CP49) and filensin (CP115), and vimentin during a mild 20-minute heat shock at 45°C. No interactions were observed with the /3or y-crystallins, or the cytoskeletal proteins actin, a-tubulin, and spectrin, although these proteins were present in lens cell homogenates. In contrast, y-crystallin and actin interacted with MBP-aB at 45°C only in their purified states. The results obtained with MBP-aB were confirmed by immunoprecipitation reactions in which immunoprecipitation of native bovine aB-crystallin from heat-shocked lens cell homogenates resulted in the coprecipitation of phakinin and filensin.