CD38 (cluster of differentiation 38), previously known as T10, is a 46 kDa type II transmembrane glycoprotein (1). CD38 is expressed in both lymphoid and non-lymphoid tissue including in thymocytes, T and B lymphocytes, myeloid cells, natural killer cells, plasma cells, erythrocytes, and additionally in cells of the brain, pancreas, muscle, and bone (1,2). Structurally, CD38 is an "L"-shape which is formed by two separate domains connected by a three peptide-chain hinge region (2). The N-terminal domain is composed of five alpha-helices and two beta strands, while the C-terminal domain contains a four-stranded parallel beta-sheet and two long and two short alpha-helices (2). The CD38 molecule is located on chromosome 4 and is 300 amino acids (aa) in length with a theoretical molecular weight of 34 kDa that functions as both a receptor and an enzyme (1-6). As a receptor, CD38 interacts with its ligand CD31, which is largely expressed in endothelial cells (2-6). As an ectoenzyme, CD38 has a role in calcium signaling and is responsible for the conversion of nicotinamide adenine dinucleotide (NAD) into adenosine diphosphate-ribose (ADPR) or cyclic ADPR and the conversion of phosphorylated NAD (NADP) into nicotinic acid adenine dinucleotide phosphate (NAADP) (2-6).
As described above, CD38 is highly expressed in plasma cells and, as a result, is a target for treating multiple myeloma (MM), the cancer of white blood cells (4,6). The anti-CD38 monoclonal antibody daratumumab is one specific treatment for MM (4,6). Daratumumab has been shown to target MM cells through antibody-dependent cellular cytotoxicity and antibody dependent cellular phagocytosis (4). Additionally, CD38 has a potential role in neurodegenerative disorders and neuroinflammation as elucidated CD38's high expression in neurons, astrocytes, and microglia along with its enzymatic role in NAD degradation (3). Reduced NAD levels is a consequence of aging and occurs during neurodegeneration (3). Furthermore, murine studies have found that CD38 deletion inhibits neuroinflammation and neurodegeneration and therefore might be a potential therapeutic target (3). Similarly, CD38 inhibitors, like quercetin and luteolin, are used to treat age-related diseases and metabolic disorders (7).
1. Malavasi, F., Funaro, A., Alessio, M., DeMonte, L. B., Ausiello, C. M., Dianzani, U., Lanza, F., Magrini, E., Momo, M., & Roggero, S. (1992). CD38: a multi-lineage cell activation molecule with a split personality. International journal of clinical & laboratory research. https://doi.org/10.1007/BF02591400
2. Malavasi, F., Deaglio, S., Funaro, A., Ferrero, E., Horenstein, A. L., Ortolan, E., Vaisitti, T., & Aydin, S. (2008). Evolution and function of the ADP ribosyl cyclase/CD38 gene family in physiology and pathology. Physiological reviews. https://doi.org/10.1152/physrev.00035.2007
3. Guerreiro, S., Privat, A. L., Bressac, L., & Toulorge, D. (2020). CD38 in Neurodegeneration and Neuroinflammation. Cells. https://doi.org/10.3390/cells9020471
4. van de Donk, N., Richardson, P. G., & Malavasi, F. (2018). CD38 antibodies in multiple myeloma: back to the future. Blood. https://doi.org/10.1182/blood-2017-06-740944
5. Lund, F. E., Cockayne, D. A., Randall, T. D., Solvason, N., Schuber, F., & Howard, M. C. (1998). CD38: a new paradigm in lymphocyte activation and signal transduction. Immunological reviews. https://doi.org/10.1111/j.1600-065x.1998.tb01573.x
6. Glaria, E., & Valledor, A. F. (2020). Roles of CD38 in the Immune Response to Infection. Cells. https://doi.org/10.3390/cells9010228
7. Rajman, L., Chwalek, K., & Sinclair, D. A. (2018). Therapeutic Potential of NAD-Boosting Molecules: The In Vivo Evidence. Cell metabolism. https://doi.org/10.1016/j.cmet.2018.02.011