Rapid cold hardening elicits changes in brain protein profiles of the flesh fly, Sarcophaga crassipalpis

Rapid cold hardening (RCH) refers to the enhanced cold tolerance acquired by a brief exposure to a moderately low temperature. Although ecological aspects of this response have been well documented in insects, less is known about the physiological and biochemical mechanisms elicited by RCH. In this study we used two-dimensional electrophoresis to detect differences in brain protein abundance in pharate adults of the flesh fly Sarcophaga crassipalpis, in response to a 2 h RCH exposure at 0 degrees C. Fourteen high abundance proteins that responded to RCH were selected for mass spectrometric identification. Three proteins that increased in abundance during RCH included ATP synthase subunit alpha, a small heat shock protein (smHsp), and tropomyosin-1 isoforms 33/34. Eleven proteins that decreased in abundance or were missing following RCH included several proteins involved in energy metabolism, protein degradation, transcription, actin binding, and cytoskeleton organization. That several proteins increased in abundance during RCH underscores the dynamics of the RCH mechanism and suggests that more than one physiological response likely contribute to RCH. The increase in ATP synthase suggests an elevation of ATP during RCH, and the smHsp increase suggests that at least one of the Hsps is actually mobilized during RCH, rather than after RCH as previously assumed.