Hierarchical Mechanochemical Switches in Angiostatin

Abstract

We wish to propose a novel mechanism by which the triggering of a biochemical signal can be controlled by the hierarchical coupling between a protein redox equilibrium and an external mechanical force. We have characterized this mechanochemical mechanism in angiostatin, and we have evidence that it can switch the access to partially unfolded structures of this protein. We have identified a metastable intermediate that is specifically accessible under thioredoxin-rich reducing conditions, like those met by angiostatin on the surface of a tumor cell. The structure of the same intermediate accounts for the unexplained antiangiogenic activity of angiostatin. These findings demonstrate a new link between redox biology and mechanically regulated processes.

Mechanomics and Physicomics in Gravisensing

“…Although this paper does not focus on the possible molecular candidates for this sensor, see for review by Hughes-Fulford (2004), as hypothesized, this molecule(s) should be able to go through some kind of conformational change. I it is likely to be found in the load-bearing regions of or near the focal adhesion complex and corresponding cytoskeletal connections as shown for cdc42 molecule (Xiang et al 2006), vinculin (Balaban et al 2001), fibronectin (Baneyx et al 2001), angiostatin (Grandi et al 2006) or PECAM-1 (Osawa et al 2002). However, other regions within the cell should not be excluded nor the possibility that due to (micro-)gravity mobile parts within the fluidic membrane might be rearranged in such a way that different reaction kinetics might become apparent.…”

The interplay between chemistry and mechanics in the transduction of a mechanical signal into a biochemical function

“…Single molecule methodologies based either on AFM or on Optical Tweezers are now making it possible not only to evaluate and compare the mechanical stability of the folding of the proteins that sustain the transmission of the mechanical signals, but also to elucidate the determinants of their mechanical properties. When these methodologies are supported by molecular dynamics simulations [11,[58][59][60]] the atomic resolution is reached in the characterization of the conformational transitions that rule the mechanical properties of the different protein molecules.…”

“…Actually, to our knowledge, no evidence of this kind of modulation of the mechanical properties of a protein has yet been reported. Both in the case of human angiostatin [11] and of artificially engineered I27 titin modules [142] containing disulfide bonds, the main barriers to mechanical unfolding have been found to be almost independent from the reduction state. In the case of V-CAM mechanical unfolding, studied by Carl et al [141], the position of the main unfolding barrier is unchanged, but its height is found to be slightly higher in the reduced state.…”

“…An example of this kind of hierarchical control of protein mechanics by a redox chemistry has been recently proposed for human angiostatin by Grandi et al [11]. Angiostatin has a strong antiangiogenic activity based on the inhibition of endothelial cell proliferation and migration.…”

“…It is therefore acting in a mechanically active environment. It is a multimodular protein composed of five independently folded kringle modules (labelled K1-K5) that also individually show different extents of antiangiogenic activities (see [11] and references therein). Each module features a characteristic triple-loop topology due to three internal disulfide bonds.…”