Leucine rich repeat-containing protein 16A (CARMIL homolog) binds F-actin capping protein (CP) with high affinity, significantly decreasing the affinity of CP for actin barbed ends. Actin polymerization occurs at the barbed end; proteins like CP that cap the barbed end inhibit elongation. Inhibition of CP therefore enhances the rate of barbed-end actin polymerization.
In cells, GFP-LRRC16A was seen to be concentrated in lamellipodia and increased the fraction of cells with large lamellipodia. Decreasing LRRC16A levels with siRNA lowered F-actin levels, decreased lamellipodia protrusion and slowed cell migration.