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Intra- and Inter-Cellular Redox Regulation in Differentiation and Stress
B- to plasma-cell differentiation is characterized by a massive expansion of the endoplasmic reticulum, finalized to sustain abundant immunoglobulin (Ig) synthesis and secretion. The increased production of disulfide-rich Ig might cause oxidative stress that could serve signalling roles in the differentiation and lifespan control of antibody-secreting cells. In fact in 2010 we discovered that terminal B-cell differentiation entails waves of H2O2 production, redox stress and reshaping of the antioxidant responses (see publications below), but the origins and the dynamics of these redox changes are still poorly understood. H2O2 – although toxic at high concentrations - can inactivate SHP1 and other phosphatases, allowing phosphorylation of downstream targets by membrane tyrosine kinases or immune receptors. Recently we and others provided evidence that water channels (e.g aquaporins 3 and 8) could serve as peroxoporins, as NOX-produced H2O2 doesn’t seem to be freely permeant through the plasma membrane. Where and how H2O2 is produced and how it can diffuse in and between cells are fundamental questions in pathophysiology and we are trying to answer to them. To investigate the regulation of H2O2 transport, we use a panel of organelle-targeted ratiometric sensors that allow us to monitor dynamic changes in living cells. In this way I can study how cells can differentiate, integrate different kind of signals and respond to stress keeping an hard look on redox environment and implications. A better definition of the intra- and inter-cellular redox circuits may shed light on the pathophysiology of stress and cancer.
Media
I selected an HyPer I29 murine B lymphoma cell line for low expression of AQP8 using a shRNA and they were tested for HyPer response to exogenous hydrogen peroxide: in control cells HyPer ratios increase (that means going from green to red in this pseudocolored movie), whilst AQP8low I29 (i29 shAQP8 H2O2.avi) do not respond, as you can see here.
These movies show I29 cells expressing HyPer, fluorescent H2O2 probe, imaged at the microscope for a few minutes with addition of 50 uM of H2O2. The chromatic scale here represents the ratio intensity: red means high ratio, so high HyPer oxidation, and blue means low ratio. Cells that were previously treated with tunicamycin for 2 hours (080312I29cytTun2h.mov) dramatically fail to respond to exogenous H2O2.
Pubblications
1.Tyrosine kinase signal modulation: a matter of H2O2 membrane permeability?
Bertolotti M, Bestetti S, Garcia-Manteiga JM, Medraño-Fernandez I, Dal Mas A, Malosio ML, Sitia R.
Antioxid Redox Signal. 2013 Mar 31.
2.On the redox control of B lymphocyte differentiation and function.
Bertolotti M, Sitia R, Rubartelli A.
Antioxid Redox Signal. 2012 May 15;16(10):1139-49. Review.
3.B- to plasma-cell terminal differentiation entails oxidative stress and profound reshaping of the antioxidant responses.
Bertolotti M, Yim SH, Garcia-Manteiga JM, Masciarelli S, Kim YJ, Kang MH, Iuchi Y, Fujii J, Vené R, Rubartelli A, Rhee SG, Sitia R.
Antioxid Redox Signal. 2010 Oct;13(8):1133-44.
4.Redox remodeling allows and controls B-cell activation and differentiation.
Vené R, Delfino L, Castellani P, Balza E, Bertolotti M, Sitia R, Rubartelli A.
Antioxid Redox Signal. 2010 Oct;13(8):1145-55.
5.CHOP-independent apoptosis and pathway-selective induction of the UPR in developing plasma cells.
Masciarelli S, Fra AM, Pengo N, Bertolotti M, Cenci S, Fagioli C, Ron D, Hendershot LM, Sitia R.
Mol Immunol. 2010 Mar;47(6):1356-65.
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