Figure 9.

LLS/TPL motif of type II keratins undergoes phosphorylation in several tissues in response to stress or mitogenic stimulation. The results reported herein for K4/5/6, and previously reported for K8 (Liao et al., 1997) are summarized schematically. Representative organs that express the indicated keratins are shown. Upon mitogenic (e.g., mitosis during psoriasis or tumor growth) or stress-mediated stimulation (e.g., UV irradiation and apoptosis), four type II keratins (K4, K5, K6, and K8) undergo phosphorylation at the LLS/TPL motif. These four keratins share the property of expression in epithelia with regenerative potential. Phosphorylation at the LLS/TPL motif is associated with keratin solubilization, filament reorganization and collapse, which may be reversible.