Search

The importance of tetraspanin proteins in regulating migration has been demonstrated in many diverse cellular systems. However, the function of the leukocyte-restricted tetraspanin CD53 remains obscure. We therefore hypothesized that CD53 plays a role in regulating leukocyte recruitment and tested this hypothesis by examining responses of CD53-deficient mice to a range of inflammatory stimuli. Deletion of CD53 significantly reduced neutrophil recruitment to the acutely inflamed peritoneal cavity. Intravital microscopy revealed that in response to several inflammatory and chemotactic stimuli, absence of CD53 had only minor effects on leukocyte rolling and adhesion in postcapillary venules. In contrast, Cd53−/− mice showed a defect in leukocyte transmigration induced by TNF, CXCL1 and CCL2, and a reduced capacity for leukocyte retention on the endothelial surface under shear flow. Comparison of adhesion molecule expression in wild-type and Cd53−/− neutrophils revealed no alteration in expression of β2 integrins, whereas L-selectin was almost completely absent from Cd53−/− neutrophils. In addition, Cd53−/− neutrophils showed defects in activation-induced cytoskeletal remodeling and translocation to the cell periphery, responses necessary for efficient transendothelial migration, as well as increased α3 integrin expression. These alterations were associated with effects on inflammation, so that in Cd53−/− mice, the onset of neutrophil-dependent serum-induced arthritis was delayed. Together, these findings demonstrate a role for tetraspanin CD53 in promotion of neutrophil transendothelial migration and inflammation, associated with CD53-mediated regulation of L-selectin expression, attachment to the endothelial surface, integrin expression and trafficking, and cytoskeletal function.

Summary Tetraspanins regulate key processes in immune cells; however, the function of the leukocyte-restricted tetraspanin CD53 is unknown. Here we show that CD53 is essential for lymphocyte recirculation. Lymph nodes of Cd53−/− mice were smaller than those of wild-type mice due to a marked reduction in B cells and a 50% decrease in T cells. This reduced cellularity reflected an inability of Cd53−/− B and T cells to efficiently home to lymph nodes, due to the near absence of L-selectin from Cd53−/− B cells and reduced stability of L-selectin on Cd53−/− T cells. Further analyses, including on human lymphocytes, showed that CD53 stabilizes L-selectin surface expression and may restrain L-selectin shedding via both ADAM17-dependent and ADAM17-independent mechanisms. The disruption in lymphocyte recirculation in Cd53−/− mice led to impaired immune responses dependent on antigen delivery to lymph nodes. Together these findings demonstrate an essential role for CD53 in lymphocyte trafficking and immunity., Graphical Abstract, Highlights • CD53 is essential for lymph node cellularity as Cd53−/− lymph nodes lack T and B cells • CD53 is essential for lymphocyte homing to lymph nodes • CD53 stabilizes L-selectin cell surface expression and may restrain shedding • Impaired lymphocyte homing leads to diminished immune responses in Cd53−/− mice, Molecular Mechanism of Behavior; Immunology; Immune Response; Specialized Functions of Cells

The importance of tetraspanin proteins in regulating migration has been demonstrated in many diverse cellular systems. However, the function of the leukocyte-restricted tetraspanin CD53 remains obscure. We therefore hypothesized that CD53 plays a role in regulating leukocyte recruitment and tested this hypothesis by examining responses of CD53-deficient mice to a range of inflammatory stimuli. Deletion of CD53 significantly reduced neutrophil recruitment to the acutely inflamed peritoneal cavity. Intravital microscopy revealed that in response to several inflammatory and chemotactic stimuli, absence of CD53 had only minor effects on leukocyte rolling and adhesion in postcapillary venules. In contrast

Contains fulltext : 152785.pdf (Publisher’s version ) (Closed access) Deciphering the molecular basis of leukocyte recruitment is critical to the understanding of inflammation. In this study, we investigated the contribution of the tetraspanin CD37 to this key process. CD37-deficient mice showed impaired neutrophil recruitment in a peritonitis model. Intravital microscopic analysis indicated that the absence of CD37 impaired the capacity of leukocytes to follow a CXCL1 chemotactic gradient accurately in the interstitium. Moreover, analysis of CXCL1-induced leukocyte-endothelial cell interactions in postcapillary venules revealed that CXCL1-induced neutrophil adhesion and transmigration were reduced in the absence of CD37, consistent with a reduced capacity to undergo beta2 integrin-dependent adhesion. This result was supported by in vitro flow chamber experiments that demonstrated an impairment in adhesion of CD37-deficient neutrophils to the beta2 integrin ligand, ICAM-1, despite the normal display of high-affinity beta2 integrins. Superresolution microscopic assessment of localization of CD37 and CD18 in ICAM-1-adherent neutrophils demonstrated that these molecules do not significantly cocluster in the cell membrane, arguing against the possibility that CD37 regulates beta2 integrin function via a direct molecular interaction. Moreover, CD37 ablation did not affect beta2 integrin clustering. In contrast, the absence of CD37 in neutrophils impaired actin polymerization, cell spreading and polarization, dysregulated Rac-1 activation, and accelerated beta2 integrin internalization. Together, these data indicate that CD37 promotes neutrophil adhesion and recruitment via the promotion of cytoskeletal function downstream of integrin-mediated adhesion.

Contains fulltext : 172274.pdf (Publisher’s version ) (Closed access) This study supports a new concept where the opposing functions of the tetraspanins CD37 and CD82 may coordinate changes in migration and Ag presentation during dendritic cell (DC) activation. We have previously published that CD37 is downregulated upon monocyte-derived DC activation, promotes migration of both skin and bone marrow derived dendritic cells (BMDCs), and restrains Ag presentation in splenic and BMDCs. In this article, we show that CD82, the closest phylogenetic relative to CD37, appears to have opposing functions. CD82 is upregulated upon activation of BMDCs and monocyte-derived DCs, restrains migration of skin and BMDCs, supports MHC class II maturation, and promotes stable interactions between T cells and splenic DCs or BMDCs. The underlying mechanism involves the rearrangement of the cytoskeleton via a differential activation of small GTPases. Both CD37(-/-) and CD82(-/-) BMDCs lack cellular projections, but where CD37(-/-) BMDCs spread poorly on fibronectin, CD82(-/-) BMDCs are large and spread to a greater extent than wild-type BMDCs. At the molecular level, CD82 is a negative regulator of RhoA, whereas CD37 promotes activation of Rac-1; both tetraspanins negatively regulate Cdc42. Thus, this study identifies a key aspect of DC biology: an unactivated BMDC is CD37(hi)CD82(lo), resulting in a highly motile cell with a limited ability to activate naive T cells. By contrast, a late activated BMDC is CD37(lo)CD82(hi), and thus has modified its migratory, cytoskeletal, and Ag presentation machinery to become a cell superbly adapted to activating naive T cells.