Key regulator of transforming growth factor beta-1 (TGFB1) specifically required for microglia function in the nervous system. Required for activation of latent TGF-beta-1 in macrophages and microglia: associates specifically via disulfide bonds with the Latency-associated peptide (LAP), which is the regulatory chain of TGFB1, and regulates integrin-dependent activation of TGF-beta-1. TGF-beta-1 activation mediated by lrrc33/nrros is highly localized: there is little spreading of TGF-beta-1 activated from one microglial cell to neighboring microglia, suggesting the existence of localized and selective activation of TGF-beta-1 by lrrc33/nrros. Belongs to the LRRC32/LRRC33 family.