Degradation of c-fos protein (c-FOS) in the cytoplasm is very rapid in vivo and constitutes a crucial regulation of the nuclear steady-state level through the control of the amount of full-length molecules available for nuclear transport. Using cytoplasmic extracts from various origins, we report herein that c-FOS degradation can be initiated in a calcium-dependent manner which involves cysteine proteases called milli- and micro-calpain. Interestingly, FOS-B, a member of the fos multigene family, as well as all members of the jun family (JUN-B, c-JUN and JUN-D) are also sensitive to calpains albeit to different extents. FRA-2, which is a c-FOS-related protein, is resistant to micro- but not to milli-calpain whereas FRA-1, another member of the fos family, is resistant to both proteases. Given the fact that a work by others (Hirai et al., 1991b) suggests that calpains can be involved in c-FOS and c-JUN degradation in vivo, our observations raises the possibility of a novel contribution to the regulation of AP-1 transcription complex activity through a differential control of the steady-state level of some of its components that involves calpains.
Differential sensitivity of FOS and JUN family members to calpains
Carillo, S.; Pariat, M.; Steff, A. M.; Roux, P.; Etienne-Julan, M.; Lorca, T.; Piechaczyk, M.
1994-06 / vol 9 / pages 1679-89
Humans; Animals; Cell Line; Proto-Oncogene Proteins c-fos/*metabolism; Rabbits; Cytoplasm/metabolism; Proto-Oncogene Proteins c-jun/*metabolism; Calcium/physiology; Calpain/*physiology