Fig 4.

JNK phosphorylation of MARCKSL1 increases actin stability. (A) To determine the effect of JNK phosphorylation on stable actin levels, MEFs expressing venus-actin in the presence or absence of GFP-tagged MARCKSL1s (or GFP-cofilin) were treated with digitonin to extract soluble proteins with minimal loss of cell membrane. Total lysate and pellet following extraction were blotted for actin and GFP as shown. (B) Quantified data from panel A are shown. (C) To determine the effect of JNK activation on actin stability, MEFs were transfected with venus-actin, MARCKSL1-GFP, and active JNK chimera MKK7-JNK1 or MKK7-JNK2 as shown. JNK activators facilitate MARCKSL1-GFP stabilization of actin. A representative blot of lysate following digitonin extraction is shown (inset). (D) Expression of active JNK chimeras in the absence of MARCKSL1 did not alter actin stability. Mean data ± SEM are shown. Significance levels: *, P < 0.05; ***, P < 0.001.