Sphingolipid Microdomains Mediate CD38 Internalization: Topography of the Endocytosis

Abstract

Plasma membranes of several cell types contain specialized microdomains (or lipid rafts) enriched in sphingolipids, cholesterol, sphingomyelin, and glycosyl-phosphatidylinositol-anchored proteins. These membrane domains are characterized by detergent insolubility at low temperatures and low buoyant density. Human CD38 is the prototype of a gene family encoding surface molecules endowed with multiple functional activities. The endocytosis of the human CD38 molecule has been investigated in normal lymphocytes and in a number ofleukemia-and lymphoma-derived celllines demonstrating that internalization after CD38 ligation is a reproducible event involving only a fraction of the whole amount of the surface molecule. This study reports the results obtained by conventional,confocal, and electron microscopy on the effects induced by the engagement of the molecule with agonistic mAb, reproducing the signals mediated by its natural ligand. The results demonstrate that the endocytosis induced as consequence of CD38 ligation is preceded by a thorough rearrangement of the cell surface with formation of glycosphingolipid-and cholesterol-rich plasma membrane microdomains. These data suggest that specialized raft microdomains might be the plasma membrane structure through which CD38 translocates at intracellular level. The CD38/lipid interactions during the coated pit formation trigger a process that generate membrane curvature, considered as the first step of CD38 endocytosis. Moreover, ultrastructural studies show that early CD38+ endosomes are pleiomorphic and contain cisternal and vesicular regions. Late endosomes exhibit a complex organisation, containing uncoupled CD38-ligand multivesicular-or multilamellarregions.

Formation and function of ceramide-enriched membrane platforms with CD38 during M1-receptor stimulation in bovine coronary arterial myocytes

“…These lipid platforms may recruit or aggregate various signaling molecules such as trimeric G proteins, small G proteins, sphingomyelin (SM), tyrosine kinases, NADPH oxidase subunits, phosphatases, and many others, resulting in the activation of different signaling pathways. Recent studies have reported that LRs are closely associated with the CD38 pathway in various lymphocytes and these LRs may be responsible for endocytosis of CD38 and the activation of certain signaling pathways (35,46). However, the identity of these LRs remains unclear, and it is also unknown whether LRs during its clustering are involved in cADPRmediated Ca 2ϩ signaling.…”

Exploiting CD38-mediated endocytosis for immunoliposome internalization

“…PMA treatment on K562 cells, on the contrary, did not lead to any increase of fluorescence, despite the induced-CD38 expression on their cell membrane. We have already proved that internalization never involves the entire amount of surface molecules, indicating the presence of two distinct pools of CD38 [5,6]. In other works, we have, moreover, demonstrated that CD38 on the surface of treated K562 cells is an active enzyme with cyclase activity [14].…”

“…However, there is no evidence that these two subsets of CD38 perform different enzymatic tasks. In previous studies, we have shown that CD38 endocytosis is preceded by extensive rearrangement of the cell surface, with the formation of glycosphingolipid-rich and cholesterol-rich plasma membrane microdomains [6]. Receptor-mediated endocytosis is essential for monoclonal antibody (mAb) therapy, as it allows the conjugation of toxins to be internalized only by target cells.…”

Contribution of NADPH Oxidase to Membrane CD38 Internalization and Activation in Coronary Arterial Myocytes

“…It appears that NOX1 and CD38 tends to colocalize in special plasma MR domains upon ET-1 stimulation and such spatial organization supports the view that NOX1-derived O 2 · − interacts with CD38 in such MR domains, which may oxidize the cysteine residues of CD38 leading to its internalization and activation. Recent studies have reported that MRs are closely associated with the CD38 pathway in various lymphocytes and that these MRs may be responsible for the endocytosis of CD38 [34], [51], [52]. Our previous studies also showed that ceramide-enriched lipid macrodomains contribute to CD38 activity to produce cADPR in CAMs [34] and that MRs platforms mediate the aggregation of membrane NADPH oxidase subunits and subsequent activation of this enzyme in bovine coronary arterial endothelial cells [53].…”