CD38, an ADP ribosyl cyclase, is a 45 kDa type II transmembrane protein having a short N-terminal cytoplasmic domain and a long C-terminal extracellular domain, expressed on the surface of various cells including macrophages, lymphocytes, and pancreatic β cells. It is known to be involved in cell adhesion, signal transduction and calcium signaling. In addition to its transmembrane form, CD38 is detectable in biological fluids in soluble forms. The mechanism by which CD38 is solubilized from the plasma membrane is not yet clarified. In this study, we found that lipopolysaccharide (LPS) induced CD38 upregulation and its extracellular release in J774 macrophage cells. Furthermore, it also increased CD38 expression at the mRNA level by activating the Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway. However, LPS decreased the levels of CD38 in the plasma membrane by releasing CD38 into the culture supernatant. LPS-induced CD38 release was blocked by the metalloproteinase-9 inhibitor indicating that MMP-9 solubilizes CD38. In conclusion, the present findings demonstrate a potential mechanism by which C38 is solubilized from the plasma membrane.

Keywords: CD38, interferon β, JAK-STAT, lipopolysaccharide, macrophages, metalloproteinase-9