Plant Hsp90 proteins interact with B-cells and stimulate their proliferation

CORIGLIANO, MARIANA G; MAGLIOCO, ANDREA; LAGUÍA BECHER, MELINA; GOLDMAN, ALEJANDRA; MARTIN, VALENTINA; ANGEL, SERGIO O; CLEMENTE, MARINA

San Luis

Congreso; 47th Annual Meeting. Argentine Society for Biochemistry and Molecular Biology Research; 2011

The molecular chaperone Hsp90 plays an important role in folding stabilization and activation of client proteins, also Hsp90 of mammals and mammalian pathogens displays immunostimulatory properties. We investigated the role of plant-derived Hsp90s as B-cell mitogens by measuring their proliferative responses in vitro. Plant cytosolic Hsp90 isoforms from Arabidopsis thaliana (AtHsp81.2) and Nicotiana benthamiana (NbHsp90.3) were expressed in E. coli. rAtHsp81.2 and rNbHsp90.3 proteins induced prominent proliferative responses in spleen cells form BALB/c mice. In vitro incubation of spleen cells with rpHsp90 led to the expansion of B lymphocytes. This effect was confirmed by immunofluorescence analysis, where a direct binding of rpHsp90 to B- but not to T-cells was observed in cells from BALB/c and C3H/HeN mice. Finally, we examined the involvement of Toll Like Receptor 4 (TLR4) in the rpHsp90s induction of B-cell proliferation. Spleen cells from C3H/HeJ mice responded poorly to prAtHsp90. However, the interaction between rpHsp90 and B-cells from C3H/HeJ mice was not altered, suggesting that the mutation on TLR4 would be affecting the signal cascade but not the rpHsp90-TLR4 receptor interaction. Our results show that spleen cell proliferation can be stimulated by a non-pathogen-derived Hsp90. Furthermore, our data provide a new example of a non-pathogen-derived ligand for TLRs.