Transmembrane 4 L6 family member 19 (TM4SF19)

Transmembrane 4 L6 family member 19 (TM4SF19) is a tetraspanin superfamily protein that localizes to lysosomal membranes, where it negatively regulates lysosomal acidification by interacting with V-ATPase subunits ATP6V0B and ATP6V0D2, thereby inhibiting V1-V0 complex assembly and vacuolar H+-ATPase activity. TM4SF19 plays a critical role in macrophage-mediated clearance of dead adipocytes and osteoclast multinucleation, with selective expression in lipid-associated and synovial macrophages. TM4SF19 is implicated in pathological mechanisms of rheumatoid arthritis, osteoporosis, and obesity, acting both through modulation of inflammation (via TLR4/MD2 signaling) and bone destruction, and is considered a candidate target for novel therapeutic interventions like LEL-Fc fusion protein, which has shown efficacy in preclinical models of inflammatory bone disease. TM4SF19 expression is also high in specific brain regions and undergoes alternative splicing, indicating broad biological significance.

Other names

OCTM4Osteoclast maturation-associated gene 4 proteinTetraspan membrane protein OCTM4TM4SF19Transmembrane 4 L6 family member 19

Competitive inhibition of TM4SF19 via LEL-Fc suppresses osteoclast differentiation by disrupting interactions with TLR4 and MD2 (involved in inflammatory signaling). Suppression of lysosomal acidification and associated cellular effects. Modulation of V-ATPase activity through altered subunit assembly.