Molecular mechanism of cytoplasmic dynein tension sensing

Abstract

Cytoplasmic dynein is the most complex cytoskeletal motor protein and is responsible for numerous biological functions. Essential to dynein’s function is its capacity to respond anisotropically to tension, so that its microtubule-binding domains bind microtubules more strongly when under backward load than forward load. The structural mechanisms by which dynein senses directional tension, however, are unknown. Using a combination of optical tweezers, mutagenesis, and chemical cross-linking, we show that three structural elements protruding from the motor domain—the linker, buttress, and stalk—together regulate directional tension-sensing. We demonstrate that dynein’s anisotropic response to directional tension is mediated by sliding of the coiled-coils of the stalk, and that coordinated conformational changes of dynein’s linker and buttress control this process. We also demonstrate that the stalk coiled-coils assume a previously undescribed registry during dynein’s stepping cycle. We propose a revised model of dynein’s mechanochemical cycle which accounts for our findings.

The Generation of Dynein Networks by Multi-Layered Regulation and Their Implication in Cell Division

“…The activity of dynein is also regulated by applied forces (Figure 1D). Several biophysical studies have shown that dynein has a characteristic force response property: it binds to a microtubule more strongly in the presence of backward loads than forward loads (Cleary et al, 2014;Nicholas et al, 2015a;Rao et al, 2019). Recently, Rao et al (2019) revealed that the asymmetric force response to directional loads is mediated by the sliding of the coiled-coils of the stalk, and that coordinated conformational changes of linker regions control this process.…”

Structural basis for two-way communication between dynein and microtubules

“…Based on the modeled conformational changes of MTBD in the absence and presence of MTs in the present study, we propose that the mechanochemical cycle of dynein proceeds via two distinctive pathways, namely an "ATPase-driven pathway" and a "MT-binding-induced pathway". In the ATP-bound states, the stalk coiled-coil adopts the +β-registry across the entire region following the linker detachment from AAA5 ( Fig.6b (2)), and MTBD is stabilized in the low-affinity state 8 (Fig. 6b (3)).…”

“…Biochemical studies have demonstrated that the sliding of CC1 with respect to CC2 by oneturn of an α−helix results in a distinctive change in the affinity for MTs 18,19 . A recent single-molecule study further demonstrated that the sliding of coiled-coil helices and the resulting changes in interaction with stalk and strut/buttress regulates the MT-binding affinity and dynein motility 8 . Comparison of the crystal structures of the motor domain in the ADP/Vi- 11 and ADP 9 -bound states have indicated that the change in the registry is caused by an altered interaction between the stalk and strut/buttress.…”

“…In addition, another coiled-coil structure, called the strut 6 or buttress 7 , extends from the AAA5 module and forms a Y-shaped structure together with the stalk coiled-coil ( Fig. 1a), and the linker also controls the conformation of the strut/buttress 8 .…”

“…Based on the previous structural and functional studies [8][9][10][11][12][13] , the mechanochemical cycle of the dynein motor is explained as follows 14,15 : (1) in the absence of the nucleotide, the motor domain is tightly bound to the MT. (2) ATP binding to the motor domain induces dissociation from the MT as well as the remodeling of the linker domain from straight to bent conformation (recovery stroke).…”