Cutting Edge: Slamf8 Is a Negative Regulator of Nox2 Activity in Macrophages.

Slamf8 (CD353) is a cell surface receptor that is expressed upon activation of macrophages (MØs) by IFN-γ or bacteria. In this article, we report that a very high NADPH oxidase (Nox2) enzyme activity was found in Slamf8-/- MØs in response to Escherichia coli or Staphylococcus aureus, as well as to PMA. The elevated Nox2 activity in Slamf-/- MØs was also demonstrated in E. coli or S. aureus phagosomes by using a pH indicator system and was further confirmed by a reduction in the enzyme activity after transfection of the receptor into Slamf8-deficient primary MØs or RAW 264.7 cells. Upon exposure to bacteria or PMA, protein kinase C activity in Slamf8-/- MØs is increased. This results in an enhanced phosphorylation of p40phox, one key component of the Nox2 enzyme complex, which, in turn, leads to greater Nox2 activity. Taken together, the data show that, in response to inflammation-associated stimuli, the inducible receptor Slamf8 negatively regulates inflammatory responses. [ABSTRACT FROM AUTHOR]