Differential sensitivity of FOS and JUN family members to calpains.
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 (Hiraï 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.
Carillo
S
S
Institut de Génétique Moléculaire de Montpellier, UMR 9942, France.
Pariat
M
M
Steff
A M
AM
Roux
P
P
Etienne-Julan
M
M
Lorca
T
T
Piechaczyk
M
M
D000818:Animals; D002118:Calcium / Q000502:physiology; D002154:Calpain / Q000502:physiology*; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D011817:Rabbits
D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D002154:Calpain; D002118:Calcium