Effect of UV Stress on the Structure and Function of Pro-apoptotic Bid and Anti-apoptotic Bcl-xl proteins.

Ultraviolet C (UV-C) radiation induces apoptosis in mammalian cells via the mitochondrion-mediated pathway. The Bcl-2 family of proteins are the regulators of the mitochondrial pathway of apoptosis and appears responsive to UV-C radiation. It is unknown how the structure and, effectively, the function of these proteins are directly impacted by UV-C exposure. Here, we present the effect of UV-C irradiation on the structure and function of pro-apoptotic Bid-FL and anti-apoptotic Bcl-xlΔC proteins. Using a variety of biophysical tools, we show that, following UV-C irradiation, the structures of Bcl-xlΔC and Bid-FL are irreversibly altered. Bcl-xLΔC is found to be more sensitive to UV stress than Bid-FL Interestingly, UV-C exposure shows dramatic chemical shift perturbations in consequence of dramatic structural perturbations (α-helix to ß-sheet) in the BH3- binding region, a crucial segment of Bcl-xlΔC. Furter it has been shown that UV-exposed Bcl-xlΔC has reduced efficacy of its interactions with pro-apoptotic tBid.

Altered hippocampal expression and function of cytosolic phospholipase A2 (cPLA2) in temporal lobe epilepsy (TLE).

OBJECTIVES: Temporal lobe epilepsy (TLE) is the most common form of drug-resistant epilepsy. Blood-brain barrier (BBB) leakage occurs during epileptogenesis and several pieces of evidence suggest that this might contribute to the progression of epilepsy. Seizures trigger a pathway involving glutamate signalling through cytosolic phospholipase A2 (cPLA2). This pathway leads to BBB leakage and induces the expression of drug efflux transporters, leading to drug resistance. Therefore, this study aims to determine the mRNA and protein levels of cPLA2, along with its functional activity, in the hippocampus of pilocarpine model of TLE as well as in the surgically resected hippocampal samples of patients with TLE. METHODS: mRNA levels and protein levels of cPLA2 were evaluated by real-time PCR and western blot analysis respectively in animal model of TLE as well as surgically resected hippocampal tissue specimens of TLE. cPLA2 functional activity was measured spectrophotometrically. RESULTS: Significant up-regulation of cPLA2 mRNA was observed in the hippocampal samples obtained from TLE rats (p < 0.05) and-TLE patients (p < 0.01). Increased protein expression of cPLA2 was also demonstrated in the hippocampal samples of TLE rats (p < 0.01) as well as TLE patients (p < 0.01). Similarly, functional activity of cPLA2 was found to be up-regulated in the hippocampus of pilocarpine model of TLE rats (p < 0.01) as well as in the TLE patients (p < 0.01). DISCUSSION: These findings suggest that alterations in cPLA2 expression and activity level in the hippocampus could potentially be a part of dynamic changes associated with TLE.