FIG. 8.

Activation of RSK3 by mitochondrial oxidants. (A) Assessment of RSK3, p70S6K, and AKT1 activity under basal conditions or following pyruvate stimulation or antimycin treatment. (Inset) In vitro phosphorylation of a GSK fusion protein using immunoprecipitated RSK3 from control (C), pyruvate (P)-, or antimycin (A)-stimulated lysate. (B) Basal and stimulated levels of RSK3 activity in cells stably expressing an approximately twofold increase in GSTpi or in control (neo)-transfected cells. (C) Levels of RSK3 activity with or without overnight pretreatment with 20 mM NAC. RSK3 activity was assessed under basal conditions (open bar) or 90 min after 100 mM pyruvate (stippled bar) or 25 μM antimycin (shaded bar) treatment. (D) Levels of RSK2 or RSK3 activity under basal conditions or after increased mitochondrial oxidant release induced by antimycin treatment. Activity was assessed in the absence (−) or presence (+) of a dominant negative SEK1 isoform.