Publications

• AQP8 transports NOX2-generated H2O2 across the plasma membrane to promote signaling in B cells.

  Bertolotti M., Farinelli G., Galli M., Aiuti A., Sitia R.

  H₂O₂ acts as a second messenger in key signaling circuits, transiently modulating tyrosine phosphatases and kinases. We investigated its origin, membrane transport, and functional role during B cell activation and differentiation. Our data identified NADPH-oxidase 2 as the ma ... >> More

  H₂O₂ acts as a second messenger in key signaling circuits, transiently modulating tyrosine phosphatases and kinases. We investigated its origin, membrane transport, and functional role during B cell activation and differentiation. Our data identified NADPH-oxidase 2 as the main source of H₂O₂ and aquaporin 8 as a transport facilitator across the plasma membrane. On aquaporin 8 silencing, inducible B lymphoma cells responded poorly to TLR and BCR stimulation. Their differentiation was severely impaired, as demonstrated by retarded onset of IgM polymerization, low amounts of IgM secretion, and prolonged BCR expression on the cell surface. A silencing-resistant aquaporin 8 rescued responsiveness, confirming that the import of H₂O₂ across the membrane is essential for B cell activation. The addition of exogenous catalase to primary B splenocytes severely impaired the tyrosine phosphorylation induced by BCR cross-linking, as did the absence of NOX2 in a murine model of chronic granulomatous disease. Importantly, re-expression of gp91^phox through gene therapy restored the specific B cell signaling deficiency in NOX2^-/- cells. Thus, efficient induction of B cell activation and differentiation requires intact H₂O₂ fluxes across the plasma membrane for signal amplification. << Less

  J. Leukoc. Biol. 100:1071-1079(2016) [PubMed] [EuropePMC]

• Laccaria bicolor aquaporin LbAQP1 is required for Hartig net development in trembling aspen (Populus tremuloides).

  Navarro-RoDenas A., Xu H., Kemppainen M., Pardo A.G., Zwiazek J.J.

  The development of ectomycorrhizal associations is crucial for growth of many forest trees. However, the signals that are exchanged between the fungus and the host plant during the colonization process are still poorly understood. In this study, we have identified the relationship between expressi ... >> More

  The development of ectomycorrhizal associations is crucial for growth of many forest trees. However, the signals that are exchanged between the fungus and the host plant during the colonization process are still poorly understood. In this study, we have identified the relationship between expression patterns of Laccaria bicolor aquaporin LbAQP1 and the development of ectomycorrhizal structures in trembling aspen (Populus tremuloides) seedlings. The peak expression of LbAQP1 was 700-fold higher in the hyphae within the root than in the free-living mycelium after 24 h of direct interaction with the roots. Moreover, in LbAQP1 knock-down strains, a non-mycorrhizal phenotype was developed without the Hartig net and the expression of the mycorrhizal effector protein MiSSP7 quickly declined after an initial peak on day 5 of interaction of the fungal hyphae with the roots. The increase in the expression of LbAQP1 required a direct contact of the fungus with the root and it modulated the expression of MiSSP7. We have also determined that LbAQP1 facilitated NO, H2 O2 and CO2 transport when heterologously expressed in yeast. The report demonstrates that the L. bicolor aquaporin LbAQP1 acts as a molecular signalling channel, which is fundamental for the development of Hartig net in root tips of P. tremuloides. << Less

  Plant Cell Environ. 38:2475-2486(2015) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Tyrosine kinase signal modulation: a matter of H2O2 membrane permeability?

  Bertolotti M., Bestetti S., Garcia-Manteiga J.M., Medrano-Fernandez I., Dal Mas A., Malosio M.L., Sitia R.

  Abstract H2O2 produced by extracellular NADPH oxidases regulates tyrosine kinase signaling inhibiting phosphatases. How does it cross the membrane to reach its cytosolic targets? Silencing aquaporin-8 (AQP8), but not AQP3 or AQP4, inhibited H2O2 entry into HeLa cells. Re-expression of AQP8 with si ... >> More

  Abstract H2O2 produced by extracellular NADPH oxidases regulates tyrosine kinase signaling inhibiting phosphatases. How does it cross the membrane to reach its cytosolic targets? Silencing aquaporin-8 (AQP8), but not AQP3 or AQP4, inhibited H2O2 entry into HeLa cells. Re-expression of AQP8 with silencing-resistant vectors rescued H2O2 transport, whereas a C173A-AQP8 mutant failed to do so. Lowering AQP8 levels affected H2O2 entry into the endoplasmic reticulum, but not into mitochondria. AQP8 silencing also inhibited the H2O2 spikes and phosphorylation of downstream proteins induced by epidermal growth factor. These observations lead to the hypothesis that H2O2 does not freely diffuse across the plasma membrane and AQP8 and other H2O2 transporters are potential targets for manipulating key signaling pathways in cancer and degenerative diseases. << Less

  Antioxid. Redox Signal. 19:1447-1451(2013) [PubMed] [EuropePMC]