Ab initio molecular dynamics of the reactivity of vitamin C toward hydroxyl and $$ {HO}_2/{O}_2^{-} $$ radicals

Vitamin C is one of the most abundant exogenous antioxidants in the cell, and it is of the utmost importance to elucidate its mechanism of action against radicals. In this study, the reactivity of vitamin C toward OH and \( {HO}_2/{O}_2^{-} \) radicals in aqueous medium was analyzed by ab initio molecular dynamics using CPMD code. The simulations led to results similar to those of static studies or experiments for the pair of \( {HO}_2/{O}_2^{-} \) radicals but bring new insights for the reactivity with hydroxyl radical: the reaction takes place before the formation of an adduct and consists of two steps: first an electron is transferred to hydroxyl radical and then the ascorbyl radical loses a proton.

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Graphical Abstract Reactivity of vitamin C toward hydroxyl and \( {HO}_2/{O}_2^{-} \) radicals

     

Integrin α8β1 regulates adhesion,migration and proliferation of human intestinal crypt cells via a predominant RhoA/ROCK‐dependent mechanism

Background. Integrins are transmembrane αβ heterodimer receptors that function as structural and functional bridges between the cytoskeleton and ECM (extracellular matrix) molecules. The RGD (arginine‐glycine‐aspartate tripeptide motif)‐dependent integrin α8β1 has been shown to be involved in various cell functions in neuronal and mesenchymal‐derived cell types. Its role in epithelial cells remains unknown. Results. Integrin α8β1 was found to be expressed in the crypt cell population of the human intestine but was absent from differentiating and mature epithelial cells of the villus. The function of α8β1 in epithelial crypt cells was investigated at the cellular level using normal HIECs (human intestinal epithelial cells). Specific knockdown of α8 subunit expression using an shRNA (small‐hairpin RNA) approach showed that α8β1 plays important roles in RGD‐dependent cell adhesion, migration and proliferation via a RhoA/ROCK (Rho‐associated kinase)‐dependent mechanism as demonstrated by active RhoA quantification and pharmacological inhibition of ROCK. Moreover, loss of α8β1, through RhoA/ROCK, impairs FA (focal adhesion) complex integrity as demonstrated by faulty vinculin recruitment. Conclusions. Integrin α8β1 is expressed in epithelial cells. In intestinal crypt cells, α8β1 is closely involved in the regulation of adhesion, migration and cell proliferation via a predominant RhoA/ROCK‐dependent mechanism. These results suggest an important role for this integrin in intestinal crypt cell homoeostasis.     

MicroRNA expression characterizes oligometastasis(es)

Background

Cancer staging and treatment presumes a division into localized or metastatic disease. We proposed an intermediate state defined by ≤5 cumulative metastasis(es), termed oligometastases. In contrast to widespread polymetastases, oligometastatic patients may benefit from metastasis-directed local treatments. However, many patients who initially present with oligometastases progress to polymetastases. Predictors of progression could improve patient selection for metastasis-directed therapy.

Methods

Here, we identified patterns of microRNA expression of tumor samples from oligometastatic patients treated with high-dose radiotherapy.

Results

Patients who failed to develop polymetastases are characterized by unique prioritized features of a microRNA classifier that includes the microRNA-200 family. We created an oligometastatic-polymetastatic xenograft model in which the patient-derived microRNAs discriminated between the two metastatic outcomes. MicroRNA-200c enhancement in an oligometastatic cell line resulted in polymetastatic progression.

Conclusions

These results demonstrate a biological basis for oligometastases and a potential for using microRNA expression to identify patients most likely to remain oligometastatic after metastasis-directed treatment.     

RNF24, a new TRPC interacting protein, causes the intracellular retention of TRPC

TRPCs function as cation channels in non-excitable cells. The N-terminal tails of all TRPCs contain an ankyrin-like repeat domain, one of the most common protein-protein interaction motifs. Using a yeast two-hybrid screening approach, we found that RNF24, a new membrane RING-H2 protein, interacted with the ankyrin-like repeat domain of TRPC6. GST pull-down and co-immunoprecipitation assays showed that RNF24 interacted with all TRPCs. Cell surface-labelling assays showed that the expression of TRPC6 at the surface of HEK 293T cells was greatly reduced when it was transiently co-transfected with RNF24. Confocal microscopy showed that TRPC3 and TRPC6 co-localized with RNF24 in a perinuclear compartment and that RNF24 co-localized with mannosidase II, a marker of the Golgi cisternae. Using a pulse-chase approach, we showed that RNF24 did not alter the maturation process of TRPC6. Moreover, in HEK 293T cells, RNF24 did not alter carbachol-induced Ca(2+) entry via endogenous channels or TRPC6. These results indicate that RNF24 interacts with TRPCs in the Golgi apparatus and affects TRPC intracellular trafficking without affecting their activity.