Activated nanoscale actin-binding domain motion in the catenin–cadherin complex revealed by neutron spin echo spectroscopy

Abstract

As the core component of the adherens junction in cell–cell adhesion, the cadherin–catenin complex transduces mechanical tension between neighboring cells. Structural studies have shown that the cadherin–catenin complex exists as an ensemble of flexible conformations, with the actin-binding domain (ABD) of α-catenin adopting a variety of configurations. Here, we have determined the nanoscale protein domain dynamics of the cadherin–catenin complex using neutron spin echo spectroscopy (NSE), selective deuteration, and theoretical physics analyses. NSE reveals that, in the cadherin–catenin complex, the motion of the entire ABD becomes activated on nanosecond to submicrosecond timescales. By contrast, in the α-catenin homodimer, only the smaller disordered C-terminal tail of ABD is moving. Molecular dynamics (MD) simulations also show increased mobility of ABD in the cadherin–catenin complex, compared to the α-catenin homodimer. Biased MD simulations further reveal that the applied external forces promote the transition of ABD in the cadherin–catenin complex from an ensemble of diverse conformational states to specific states that resemble the actin-bound structure. The activated motion and an ensemble of flexible configurations of the mechanosensory ABD suggest the formation of an entropic trap in the cadherin–catenin complex, serving as negative allosteric regulation that impedes the complex from binding to actin under zero force. Mechanical tension facilitates the reduction in dynamics and narrows the conformational ensemble of ABD to specific configurations that are well suited to bind F-actin. Our results provide a protein dynamics and entropic explanation for the observed force-sensitive binding behavior of a mechanosensitive protein complex.

Applications of neutron spin echo in soft matter

“…The mechanical adhesion coupling exhibited in this complex holds significant physiological implications. They devised six distinct component models, identified the most appropriate model via comparative analysis, and successfully delineated each constituent's dynamic contributions, thus elucidating the interplay between protein complex domains and their role as force sensors [52].…”

Q-dependent collective relaxation dynamics of glass-forming liquid Ca0.4K0.6(NO3)1.4 investigated by wide-angle neutron spin-echo

“…This crossover occurs in the Q -range of the first minimum above the primary peak of the structure factor S ( Q ), but around the primary peak it is either not observed 21 , 22 or is too weak to be appreciated 23 , due to the local length scale of the JG β-process. The technique of NSE, which encodes the dynamic signal in the spin of the neutrons and measures the Q -dependent intermediate scattering function (ISF) directly in time domain, offers the highest energy resolution among all neutron spectroscopy techniques and thus has been extensively employed for studying the relaxation dynamics of a wide variety of materials on the pico- to nanosecond time scale 19 , 24 – 36 . Traditional NSE instruments only measure one Q at a time, thus limiting the number of accessible Q values in a given experiment.…”

Variation of Structural and Dynamical Flexibility of Myelin Basic Protein in Response to Guanidinium Chloride

“…Small-angle scattering by X-rays and neutrons (SAXS/SANS) as well as neutron spin-echo spectroscopy (NSE) have been used to provide information on structure and dynamics of MBP, respectively, in response to GndCl concentration. The combination of those techniques has been applied previously for the investigation of unfolded and partially folded proteins in solution [21,22,26,27] revealing the intricate connection between structural constraints on protein fluctuations.…”