Recently using the novel ligand-receptor capture method, and mammalian-cell expressed CTRP3, Li et al. (2016) (41) identified Lysosomal-associated membrane protein 1 (LAMP-1) and Lysosome membrane protein 2 (LIMP II) as potential receptors for CTRP3. Although it remains to be determined whether either of these proteins directly mediate the intercellular effects of CTRP3 or act as coreceptors for a yet unidentified protein, both LAMP1 and LIMPII are widely expressed in a number of different tissues corresponding to the variety of functions attributed to CTRP3. A comprehensive list of in vitro functions documented for CTRP3 is listed in Table 2. CTRP3 may also act without directly initiating intracellular action but rather through inhibiting the binding of other ligands. For example, lipopolysaccharide (LPS) is a potent endotoxin that binds to Toll-like receptor 4 (TLR4) and promotes a cellular inflammatory response. However, even though CTRP3 does not bind directly to either LPS or TLR4, CTRP3 prevents their interaction through an unestablished mechanism (30).
