Phagocytosis depends on TRPV2-mediated calcium influx and requires TRPV2 in lipids rafts: alteration in macrophages from patients with cystic fibrosis.

Whereas many phagocytosis steps involve ionic fluxes, the underlying ion channels remain poorly defined. As reported in mice, the calcium conducting TRPV2 channel impacts the phagocytic process. Macrophage phagocytosis is critical for defense against pathogens. In cystic fibrosis (CF), macrophages have lost their capacity to act as suppressor cells and thus play a significant role in the initiating stages leading to chronic inflammation/infection. In a previous study, we demonstrated that impaired function of CF macrophages is due to a deficient phagocytosis. The aim of the present study was to investigate TRPV2 role in the phagocytosis capacity of healthy primary human macrophage by studying its activity, its membrane localization and its recruitment in lipid rafts. In primary human macrophages, we showed that P. aeruginosa recruits TRPV2 channels at the cell surface and induced a calcium influx required for bacterial phagocytosis. We presently demonstrate that to be functional and play a role in phagocytosis, TRPV2 might require a preferential localization in lipid rafts. Furthermore, CF macrophage displays a perturbed calcium homeostasis due to a defect in TRPV2. In this context, deregulated TRPV2-signaling in CF macrophages could explain their defective phagocytosis capacity that contribute to the maintenance of chronic infection

Association of CD147 and Calcium Exporter PMCA4 Uncouples IL-2 Expression from Early TCR Signaling

The Ig superfamily member CD147 is upregulated following T cell activation and was shown to serve as a negative regulator of T cell proliferation. Thus, Abs targeting CD147 are being tested as new treatment strategies for cancer and autoimmune diseases. How CD147 mediates immunosuppression and whether association with other coreceptor complexes is needed have remained unknown. In the current study, we show that silencing of CD147 in human T cells increases IL-2 production without affecting the TCR proximal signaling components. We mapped the immunosuppressive moieties of CD147 to its transmembrane domain and Ig-like domain II. Using affinity purification combined with mass spectrometry, we determined the domain specificity of CD147 interaction partners and identified the calcium exporter plasma membrane calcium ATPase isoform 4 (PMCA4) as the interaction partner of the immunosuppressive moieties of CD147. CD147 does not control the proper membrane localization of PMCA4, but PMCA4 is essential for the CD147-dependent inhibition of IL-2 expression via a calcium-independent mechanism. In summary, our data show that CD147 interacts via its immunomodulatory domains with PMCA4 to bypass TCR proximal signaling and inhibit IL-2 expression