Reversible translocation of ASK1 to a Triton-X100 insoluble cytoplasmic compartment during cardiac myocyte cell stress.

ASK1 is a cellular stress-responsive MAPKKK which activates the JNK and p38 MAPK pathways that play a key role in the response of cardiac myocytes to redox stress following ischemia/reperfusion. ASK1 becomes incorporated into high-molecular weight complexes upon activation but this has not been investigated in cardiac myocytes. Here we examine the distribution of ASK1 in neonatal rat cardiomyocytes undergoing simulated ischemia and reperfusion. Simulated ischemia or redox stress in neonatal cardiac myocytes causes the translocation of ASK1 to distinct punctate cytoplasmic structures that are insoluble in Triton X-100. The translocation event is not dependent on ASK1 kinase activity, occurs subsequent to activation and is reversible upon removal of the cell stress. The structures to which ASK1 translocates in cardiac myocytes do not appear to correspond to the previously described ASK1 signalosome reported in other cell types.