Fig 7.
JNK phosphorylation sites on MARCKSL1 are important for filopodium formation and motility. (A) Snapshots of cortical neurons expressing MARCKSL1-GFP phosphorylation site variants are shown. Cells expressing MARCKSL1-AAA typically displayed large lamellipodia and very few if any filopodium-enriched regions. Conversely, cells expressing MARCKSL1-DDD displayed prominent and long filopodia. Time-lapse movies of these fields of view are available in the supplemental material. (B) Quantitative data on filopodial numbers from neurons expressing MARCKSL1-WT, MARCKSL1-AAA, or MARCKSL1-DDD are shown. (C) To quantify filopodial dynamics, maximum-intensity projections representing sequentially subtracted images were used to provide an index of motility. Increased intensity reflects increased movements. Cells expressing MARCKSL1-DDD or the WT showed greater filopodial dynamics. (D) Quantitative data depicting integrated densities from multiple maximum-intensity projections, as depicted in panel C, are shown. Data represent means ± SEM. Significance levels: **, P < 0.01; ***, P < 0.001.