[Show abstract][Hide abstract] ABSTRACT: FKBP51 (FKBP5 Official Symbol) is a large molecular weight component of the family of FK506 binding proteins (FKBP). In recent years, research studies from our laboratory highlighted functions for FKBP51 in the control of apoptosis and melanoma progression. FKBP51 expression correlated with the invasiveness and aggressiveness of melanoma. Since a role for TGF-beta in the enhanced tumorigenic potential of melanoma cells is widely described, we hypothesized a cooperative effect between FKBP51 and TGF-beta in melanoma progression.
SAN and A375 melanoma cell lines were utilized for this study. Balb/c IL2gamma NOD SCID served to assess the ability to colonize organs and metastasize of different cell lines, which was evaluated by in vivo imaging. Realtime PCR and western blot served for measurement of mRNA and protein expression, respectively.
By comparing the metastatic potential of two melanoma cell lines, namely A375 and SAN, we confirmed that an increased capability to colonize murine organs was associated with increased levels of FKBP51. A375 melanoma cell line expressed FKBP51 mRNA levels 30-fold higher in comparison to the SAN mRNA level and appeared more aggressive than SAN melanoma cell line in an experimental metastasis model. In addition, A375 expressed, more abundantly than SAN, the TGF-beta and the pro angiogenic TGF-beta receptor type III (TbetaRIII) factors. FKBP51 silencing produced a reduction of TGF-beta and TbetaRIII gene expression in A375 cell line, in accordance with previous studies. We found that the inducing effect of TGF-beta on Sparc and Vimentin expression was impaired in condition of FKBP51 depletion, suggesting that FKBP51 is an important cofactor in the TGF-beta signal. Such a hypothesis was supported by co immunoprecipitation assays, showing that FKBP51 interacted with either Smad2,3 and p300. In normal melanocytes, FKBP51 potentiated the effect of TGF-beta on N-cadherin expression and conferred a mesenchymal-like morphology to such round-shaped cells.
Overall, our findings show that FKBP51 enhances some pro oncogenic functions of TGF-beta, suggesting that FKBP51-overexpression may help melanoma to take advantage of the tumor promoting activities of the cytokine.
Clinical and translational medicine. 01/2014; 3(1):1.
[Show abstract][Hide abstract] ABSTRACT: Monocyte/macrophages represent the first line of defense against protozoan parasites. Different mechanisms of monocyte suppression
by Toxoplasma gondii that sustain parasite invasion and persistence have been described, including apoptosis. In the present study, we investigated
the effect of microbial excretory–secretory polypeptides, namely the microneme protein MIC3 and the dense granule antigen
GRA1, on apoptosis of monocytes from patients with congenital toxoplasmosis and healthy individuals. We found that GRA1 but
not MIC3 could induce apoptosis of monocytes, observing the effect in samples from both Toxoplasma-infected and uninfected individuals, thus ruling out involvement of mechanisms of apoptosis linked to adaptive immunity or
a cellular context related to infection. Selective inhibition of TGF-β type I receptors reversed GRA1-induced apoptosis, indicating
that this apoptosis involved canonical TGF-β signaling. By using TGF-β-neutralizing antibodies, we showed that monocyte apoptosis
required endogenous TGF-β and that GRA1 stimulation activated TGF-β transcription and expression in monocytes but not lymphocytes,
suggesting involvement of an autocrine TGF-β-mediated mechanism in GRA1-induced apoptosis.