Regulation of MARCKS and MARCKS‐related protein expression in BV‐2 microglial cells in response to lipopolysaccharide

Myristoylated alanine‐rich C kinase substrate (MARCKS) and MARCKS‐related protein (MRP) have been implicated in membrane‐cytoskeletal events underlying cell adhesion, migration, secretion, and phagocytosis. In BV‐2 microglial cells, lipopolysaccharide (LPS) elicited a dose‐dependent increase in mRNA of both MRP (sixfold) and MARCKS (threefold) with corresponding increases in [3H]myristoylated and immunoreactive protein levels. LPS also produced significant increases in protein kinase C (PKC)‐β twofold and PKC‐ε (1.5‐fold). Pro‐inflammatory cytokines produced by activated microglia (IL‐1β, IL‐6, TNF‐α) did not mimic LPS effects on MARCKS or MRP expression when added individually or in combination. LPS and IFN‐γ produced a synergistic induction of iNOS but not MARCKS or MRP. Induction of MARCKS and MRP by LPS was completely blocked by inhibitors of NF‐κB (PDTC) and protein tyrosine kinases (herbimycin A), partially blocked by the p38 kinase inhibitor SB203580, and unaffected by the MEK inhibitor PD98059. LPS induction of iNOS was considerably more sensitive to all these inhibitors. The Src kinase inhibitor PP2 had no effect, while the closely related inhibitor PP1 actually increased LPS induction of MARCKS and MRP. Our results suggest that MARCKS and MRP may play an important role in LPS‐activated microglia, but are not part of the neuroinflammatory response produced by cytokines.