Cross-talk between the calcium channel TRPV4 and reactive oxygen species interlocks adhesive and degradative functions of invadosomes

Invadosomes support cell invasion by coupling both acto-adhesive and extracellular matrix degradative functions, which are apparently antagonistic. β1-integrin dynamics regulate this coupling, but the actual sensing mechanism and effectors involved have not yet been elucidated. Using genetic and reverse genetic approaches combined with biochemical and imaging techniques, we now show that the calcium channel TRPV4 colocalizes with β1-integrins at the invadosome periphery and regulates its activation and the coupling of acto-adhesive and degradative functions. TRPV4-mediated regulation of podosome function depends on its ability to sense reactive oxygen species (ROS) in invadosomes’ microenvironment and involves activation of the ROS/calcium-sensitive kinase Ask1 and binding of the motor MYO1C. Furthermore, disease-associated TRPV4 gain-of-function mutations that modulate ECM degradation are also implicated in the ROS response, which provides new perspectives in our understanding of the pathophysiology of TRPV4 channelopathies.     

Probing the reactivity of singlet oxygen with purines

The reaction of singlet molecular oxygen with purine DNA bases is investigated by computational means. We support the formation of a transient endoperoxide for guanine and by classical molecular dynamics simulations we demonstrate that the formation of this adduct does not affect the B-helicity. We thus identify the guanine endoperoxide as a key intermediate, confirming a low-temperature nuclear magnetic resonance proof of its existence, and we delineate its degradation pathway, tracing back the preferential formation of 8-oxoguanine versus spiro-derivates in B-DNA. Finally, the latter oxidized 8-oxodGuo product exhibits an almost barrierless reaction profile, and hence is found, coherently with experience, to be much more reactive than guanine itself. On the contrary, in agreement with experimental observations, singlet-oxygen reactivity onto adenine is kinetically blocked by a higher energy transition state.