Background: NMAAP1 plays a role in regulating macrophage differentiation to the M1
type and exerting antitumoral functions. It is not clear what role and mechanism NMAAP1 does
play in the reversal of macrophages from M1 to M2.
Methods: We detected the typing of macrophages with high or low expression of NMAAP1 by
QPCR and ELISA, and detected the colocalization of NMAAP1 and endogenous IP3R by laser
confocal microscopy, and detected the protein expression in cells by Western-blotting.
Results: Our study found that knockdown NMAAP1 in RAW264.7 cells induced macrophage
polarization to the M2 type and up-regulation of NMAAP1 in RAW264.7 cells maintain M1
Phenotype even in the presence of IL-4, a stronger inducer of the M2 type. Additionally, Coimmunoprecipitation
revealed a protein-protein interaction between NMAAP1 and IP3R and then
activates key molecules in the PKC-dependent Raf/MEK/ERK and Ca2+/CaM/CaMKII signaling
pathways. Activation of PKC (Thr638/641), ERK1/2 (Thr202/Tyr204) and CaMKII (Thr286) is
involved in the regulation of cell differentiation.
Conclusion: NMAAP1 interacts with IP3R, which in turn activates the PKC-dependent
Raf/MEK/ERK and Ca2+/CaM/CaMKII signaling pathways. These results provide a new
explanation of the mechanism underlying M1 differentiation.