Biology subjects

Rizza, S.

Publications and source records attributed to Rizza, S..

3 recordsLinked to original sources

bioRxiv2024

Disulfide-mediated tetramerization of TRAP1 fosters its antioxidant and pro-neoplastic activities.

The mitochondrial chaperone TRAP1 exerts a protective function in cells exposed to diverse stress conditions in both physiological and pathological contexts. In cancer cells, it contributes to neoplastic progression ensuing metabolic rewiring and protection from oxidative insults. TRAP1 works as a homodimer, but recent evidence has indicated that it can form tetramers whose functional effects remain elusive. Here, we find that TRAP1 forms redox-sensitive tetramers via disulfide bonds involving two critical cysteine residues, C261 and C573. TRAP1 tetramerization is elicited by oxidative stress and abrogated upon expression of the double C261S/C573R mutant. In cancer contexts, the expression of the TRAP1 C261S/C573R mutant is unable to inhibit the activity of its client succinate dehydrogenase and to confer protection against oxidative insults, and it hampers invasiveness of aggressive sarcoma cells. Our data indicate that TRAP1 undergoes tetramerization in response to oxidative stress and identify C261 and C573 as critical for TRAP1 structural rearrangement and for functions.

cell biology↗

bioRxiv2019

Mitophagy contributes to alpha-tocopheryl succinate toxicity in GSNOR-deficient hepatocellular carcinoma.

The denitrosylating enzyme S-nitrosoglutathione reductase (GSNOR), has been reported to control the selective degradation of mitochondria through mitophagy, by modulating the extent of nitric oxide-modified proteins (S-nitrosylation). The accumulation of S-nitrosylated proteins due to GSNOR downregulation is a feature of hepatocellular carcinoma, causing mitochondrial defects that sensitize these tumors to mitochondrial toxins, in particular to mitochondrial complex II inhibitor alpha-tocopheryl succinate (TOS). However, it is not known if mitophagy defects contribute to GSNOR-deficient cancer cells sensitivity to TOS, nor if mitophagy inhibition could be used as a common mechanism to sensitize liver cancers to this toxin. Here, we provide evidence that GSNOR-deficient cancer cells show defective mitophagy. Furthermore, we show that TOS is a mitophagy inducer and that mitophagy defects of GSNOR-deficient liver cancer cells contribute to its toxicity. We finally prove that the inhibition of mitophagy by depletion of Parkin, a pivotal ubiquitin ligase targeting mitochondria for degradation, enhances TOS toxicity, thus suggesting that this drug could be effective in treating mitophagy-defective tumors.

cancer biology↗

bioRxiv2019

S-nitrosylation affects TRAP1 structure and ATPase activity and modulates cell response to apoptotic stimuli

The mitochondrial chaperone TRAP1 has been involved in several mitochondrial functions, and modulation of its expression/activity has been suggested to play a role in the metabolic reprogramming distinctive of cancer cells. TRAP1 posttranslational modifications, i.e. phosphorylation, can modify its capability to bind to different client proteins and modulate its oncogenic activity. Recently, it has been also demonstrated that TRAP1 is S-nitrosylated at Cys501, a redox modification associated with its degradation via the proteasome. Here we report molecular dynamics simulations of TRAP1, together with analysis of long-range structural communication, providing a model according to which Cys501 S-nitrosylation induces conformational changes to distal sites in the structure of the protein. The modification is also predicted to alter open and closing motions for the chaperone function. By means of colorimetric assays and site directed mutagenesis aimed at generating C501S variant, we also experimentally confirmed that selective S-nitrosylation of Cys501 decreases ATPase activity of recombinant TRAP1. Coherently, C501S mutant was more active and conferred protection to cell death induced by staurosporine. Overall, our results provide the first in silico, in vitro and cellular evidence of the relevance of Cys501 S-nitrosylation in TRAP1 biology.

biochemistry↗