Protein-tyrosine Phosphatase Shp2 Positively Regulates Macrophage Oxidative Burst

Macrophages are vital to innate immunity and express pattern recognition receptors and integrins for the rapid detection of invading pathogens. Stimulation of Dectin-1 and complement receptor 3 (CR3) activates Erk- and Akt-dependent production of reactive oxygen species (ROS). Shp2, a protein-tyrosine phosphatase encoded by Ptpn11, promotes activation of Ras-Erk and PI3K-Akt and is crucial for hematopoietic cell function; however, no studies have examined Shp2 function in particulate-stimulated ROS production. Maximal Dectin-1-stimulated ROS production corresponded kinetically to maximal Shp2 and Erk phosphorylation. Bone marrow-derived macrophages (BMMs) from mice with a conditionally deleted allele of Ptpn11 (Shp2(flox/flox); Mx1Cre+) produced significantly lower ROS levels compared with control BMMs. Although YFP-tagged phosphatase dead Shp2-C463A was strongly recruited to the early phagosome, its expression inhibited Dectin-1- and CR3-stimulated phospho-Erk and ROS levels, placing Shp2 phosphatase function and Erk activation upstream of ROS production. Further, BMMs expressing gain of function Shp2-D61Y or Shp2-E76K and peritoneal exudate macrophages from Shp2D61Y/+; Mx1Cre + mice produced significantly elevated levels of Dectin-1- and CR3-stimulated ROS, which was reduced by pharmacologic inhibition of Erk. SIRP alpha (signal regulatory protein alpha) is a myeloid inhibitory immunoreceptor that requires tyrosine phosphorylation to exert its inhibitory effect. YFP-Shp2C463A-expressing cells have elevated phospho-SIRP alpha levels and an increased Shp2-SIRP alpha interaction compared with YFP-WT Shp2-expressing cells. Collectively, these findings indicate that Shp2 phosphatase function positively regulates Dectin-1-and CR3-stimulated ROS production in macrophages by dephosphorylating and thus mitigating the inhibitory function of SIRP alpha and by promoting Erk activation.