Key regulator of transforming growth factor beta-1 (TGFB1) specifically required for microglia function in the nervous system (By similarity). 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 (By similarity). 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 (By similarity). Indirectly plays a role in Toll-like receptor (TLR) signaling: ability to inhibit TLR-mediated NF-kappa-B activation and cytokine production is probably a consequence of its role in TGF-beta-1 signaling (PubMed:23545260). Interacts with TGFB1; associates via disulfide bonds with the Latency-associated peptide chain (LAP) regulatory chain of TGFB1, leading to regulate activation of TGF-beta-1 (PubMed:29909984). Interacts (via LRR repeats) with TLR2, TLR3, TLR4, TLR9 and probably other Toll-like receptors (PubMed:23545260). Interacts with CYBB/NOX2; the interaction is direct (By similarity). Mainly expressed in cells of hematopoietic origin (PubMed:29909984). Highly expressed in bone marrow, thymus, liver, lung, intestine and spleen (PubMed:23545260). In the brain, highly expressed in microglia (PubMed:32100099). The protein represented in this entry is involved in disease pathogenesis. Belongs to the LRRC32/LRRC33 family.