Ventricular myosin modifies in vitro step-size when phosphorylated
JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY
Authors: Wang, Yihua; Ajtai, Katalin; Burghardt, Thomas P.
Abstract
Cardiac and skeletal muscle myosins have the central role in contraction transducing ATP free energy into the mechanical work of moving actin. Myosin has a motor domain containing ATP and actin binding sites and a lever-arm that undergoes rotation impelling bound actin. The lever-arm converts torque generated in the motor into the linear displacement known as step-size. The myosin lever-arm is stabilized by bound essential and regulatory light chains (ELC and RLC). RLC phosphorylation at S15 is linked to modified lever-arm mechanical characteristics contributing to myosin filament based contraction regulation and to the response of the muscle to disease. Myosin step-size was measured using a novel quantum dot (Qdot) assay that previously confirmed a 5 nm step-size for fast skeletal myosin and multiple unitary steps, most frequently 5 and 8 nm, and a rare 3 nm displacement for beta cardiac myosin (beta Mys). S15 phosphorylation in beta Mys is now shown to change stepsize distribution by advancing the 8 nm step frequency. After phosphorylation, the 8 nm step is the dominant myosin step-size resulting in significant gain in the average step-size. An increase in myosin step-size will increase the amount of work produced per ATPase cycle. The results indicate that RLC phosphorylation modulates work production per ATPase cycle suggesting the mechanism for contraction regulation by the myosin filament. (C) 2014 Elsevier Ltd. All rights reserved.
Maysin plays a protective role against alpha-Synuclein oligomers cytotoxicity by triggering autophagy activation
FOOD AND CHEMICAL TOXICOLOGY
Authors: Leri, Manuela; Vasarri, Marzia; Palazzi, Luana; Barletta, Emanuela; Nielsen, Erik; Bucciantini, Monica; Degl'Innocenti, Donatella
Abstract
Parkinson's disease (PD) is a widespread neurodegenerative disorder characterized by the progressive loss of neurons. The accumulation of aggregated forms of the alpha-Synuclein (Syn) protein is the main cause of neumtoxicity in PD by disrupting cellular homeostasis until neuronal death. Scientific research is constantly looking for natural products as preventive agents against the progression of several neurodisorders due their safety and non-toxic nature. Neumprotective phytochemicals include Maysin (Mys), the most abundant C-glycosilflavone in corn silk. In this work, the Mys protective role against damage by Syn amyloid aggregates - oligomers and fibrils was investigated in SH-SY5Y human neuroblastoma cells obtaining novel and interesting information concerning the Mys molecular mechanism of action. Mys showed effectiveness in preventing the typical toxic events induced by Syn amyloid aggregates, i.e. oxidative stress and imbalance of intracellular calcium homeostasis. Mys exhibited a cytopmtective role, especially against Syn oligomers injury, activating an autophagic degradative process, thus playing a key role on several features of amyloid neurotoxicity. Therefore, Mys could be proposed for the first time to the scientific community as an interesting novel natural compound that might allow to develop alternative strategies to prevent the damage of Syn oligomers involved in Parkinson's disease.