Protein Tyrosine Phosphatase, Shp2, Positively Regulates Macrophage Oxidative Burst [Cell Biology]

December 23rd, 2014 by Li, X. J., Goodwin, C. B., Nabinger, S. C., Richine, B. M., Yang, Z., Hanenberg, H., Ohnishi, H., Matozaki, T., Feng, G.-S., Chan, R. J.

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 (Shp2flox/flox;Mx1Cre+) produced significantly lower ROS levels compared to control BMMs. Although yellow fluorescent protein (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 (GOF) Shp2-D61Y or Shp2-E76K and peritoneal exudate macrophages (PEMs) from Shp2D61Y/+;Mx1Cre+ mice produced significantly elevated levels of Dectin-1- and CR3-stimulated ROS which was reduced by pharmacologic inhibition of Erk. Signal regulatory proteinα (SIRPα) is a myeloid inhibitory immunoreceptor that requires tyrosine phosphorylation to exert its inhibitory effect. YFP-Shp2C463A-expressing cells have elevated phospho-SIRPα levels and an increased Shp2-SIRPα interaction compared to 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 de-phosphorylating and thus mitigating the inhibitory function of SIRPα and by promoting Erk activation.