Dynamics of ATP-dependent and ATP-independent steppings of myosin-V on actin: catch-bond characteristics

Embryonic exposure to aluminum chloride blocks the onset of spermatogenesis through disturbing the dynamics of testicular tight junctions via upregulating Slc25a5 in offspring

Studies have revealed neurotoxicity, hepatotoxicity, and developmental and reproductive toxicity in mice exposed to aluminum. However, relatively few studies have been conducted to clarify the mechanism underlying the impact of embryonic exposure to aluminum on the development of the male reproductive system in offspring. Pregnant mice were administered aluminum chloride (AlCl3) by gavage from day 12.5 of gestation until birth. Our findings demonstrated that embryonic exposure to AlCl3 disrupted testicular development and spermatogenesis by impairing testicular architecture, reducing sperm count, and upregulating the expression of tight junction (TJ) protein between Sertoli cells (SCs). Further in vitro studies revealed that treatment with AlCl3 stabilized TJ proteins Occludin and ZO-1 expression by inhibiting ERK signaling pathway activation, thereby upregulating Slc25a5 expression which induced ATP production leading to disruption of cytoskeletal protein homeostasis. Therefore, the study provided a new mechanistic insight into how AlCl3 exposure interfered with testicular development and spermatogenesis while suggesting that Slc25a5 might be a target affected by AlCl3 influencing cell metabolism.

Memory induced-mechanism of noise attenuator of myosin V molecular motors

Depending on the chemical energy from ATP hydrolysis, myosin V can drive the multistep and continuous coupled cycling process to transport cellular cargo to targeted regions. However, it is still obscure how the molecular memory induced by the multistep coupled transported process could regulate the dynamic behavior of the motor state of myosin V. Here, we propose a novel non-Markovian polymorphic mechanochemical model to investigate the effect of the molecular memory on the mechanic of noise attenuation of myosin V system. We first define an effective transition rate for a multistep coupled reaction process which is the function of memory and system states to transform equivalently the non-Markovian process into the classical Markov process. By noise decomposition technology, it is observed that both the intrinsic and extrinsic noises of the ADP-myosin V bound state (AM ⋅ ADP) exhibit a monotonically decreasing trend with lengthening the molecular memory. Molecular memory as a regulation factor can amplify the contribution of intrinsic noise to the overall noise while reducing the influence of extrinsic noise on the AM ⋅ ADP. Moreover, the modulation of molecular memory could induce stochastic focusing. These results indicate that the role of molecular memory in the myosin V state transition can not only offer a handle to maintain the robustness of the motion system but also serve as a paradigm for studying more complex molecular motors.

Modeling Study of the Dynamics of Kinesin-14 Molecular Motors

Kinesin-14s constitute a subfamily of the large superfamily of adenosine triphosphate-dependent microtubule-based motor proteins. Kinesin-14s have the motor domain at the C-terminal end of the peptide, playing key roles during spindle assembly and maintenance. Some of them are nonprocessive motors, whereas others can move processively on microtubules. Here, we take budding yeast Cik1-Kar3 and human HSET as examples to study theoretically the dynamics of the processive kinesin-14 motor moving on the single microtubule under load, the dynamics of the motor coupled with an Ndc80 protein moving on the single microtubule, the dynamics of the motor moving in microtubule arrays, and so on. The dynamics of the nonprocessive Drosophila Ncd motor is also discussed. The studies explain well the available experimental data and, moreover, provide predicted results. We show that the processive kinesin-14 motors can move efficiently in microtubule arrays toward the minus ends, and after reaching the minus ends, they can stay there stably, thus performing the function of organizing the microtubules in the bipolar spindle into polar arrays at the spindle poles.