MAPK3 and ischemia: Since the impact of cardiac ischemia on phosphorylation of EGFR and ERB2 as well as their downstream signaling molecules is not known, we next showed that hearts subjected to ischemia led to a reduction in EGFR and erbB2 phosphorylation as well as that of the known downstream effectors, ERK1/2 and p38 MAP kinases (Figure 6).