MARCKS N-terminal sequence-derived inhibitor peptides impair monocytic ROS production and migration via MARCKS-independent effects

Abstract Background Myristoylated alanine-rich C kinase substrate (MARCKS) is a versatile unstructured protein involved in numerous cellular processes and associated with various diseases. In this study, the effect of MARCKS’ N-terminal sequence-derived inhibitor peptides MANS (“myristoylated N-terminal sequence”) and BIO-11006 on monocytic ROS production and migration was assessed. Methods and results Stimulation of calcitriol-differentiated monocytic THP-1 cells with PMA, opsonized (ops.) E. coli, ops. S. aureus, and ops. zymosan led to considerable ROS production (as determined using a chemiluminescence-based assay), an effect significantly reduced in THP-1-derived MARCKS knock-out (KO) cells that were generated with the CRISPR/Cas9 technique. MANS similarly inhibited ROS production in monocytic THP-1 and PLB-985 cells as well as primary human monocytes induced by various stimuli, while BIO-11006 predominantly affected PMA-induced ROS levels. TNF preincubation enhanced monocytic ROS production, but was not able to compensate for MANS treatment or MARCKS deficiency. Unexpectedly, an inhibition of ROS formation by both inhibitor peptides could also be observed in MARCKS KO cells, indicating a target-independent effect of MANS and BIO-11006 at least in MARCKS-deficient monocytic cells. Comparable negative effects of MANS in both WT and KO cells could also be observed when monocytic migration was assessed in transwell assays. Conclusion Our data suggest that MARCKS inhibitor peptides MANS and (to a lesser extent) BIO-11006 are able to inhibit MARCKS-associated cellular processes in monocytic cells by MARCKS-independent mechanisms.