Prolonged cross-bridge binding triggers muscle dysfunction in a Drosophila model of myosin-based hypertrophic...

Area of Science:

• Cardiovascular Biology
• Muscle Physiology
• Biochemistry

Background:

• Hypertrophic cardiomyopathy (HCM) is a genetic heart disease often caused by mutations in cardiac myosin.
• The K146N mutation in human beta-cardiac myosin is a known cause of HCM.
• Understanding the molecular mechanisms underlying HCM is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the functional consequences of the K146N mutation in Drosophila melanogaster.
• To elucidate the biochemical, physiological, and mechanical underpinnings of K146N-induced cardiomyopathy.
• To explore the utility of Drosophila as a model system for HCM research.

Main Methods:

• Biochemical assays including ATPase activity and actin motility assays.
• Physiological and mechanical measurements of Drosophila indirect flight muscle.
• Analysis of sarcomere morphology and cardiac function in Drosophila models.

Main Results:

• The K146N mutation alters cross-bridge cycle kinetics, increasing myosin attachment and decreasing detachment rates, leading to prolonged cross-bridge binding.
• Prolonged binding enhances isometric force but impairs dynamic contraction, reducing work, power output, and flight ability.
• Drosophila hearts with the K146N mutation exhibit hypercontractility, increased tension, reduced chamber dimensions, and myofibrillar disarray, mirroring human HCM phenotypes.

Conclusions:

• Prolonged cross-bridge binding is a key mechanistic basis for K146N-induced hypertrophic cardiomyopathy.
• Drosophila serves as a valuable model for studying HCM, enabling rapid screening of disease-causing alleles and potential therapeutic interventions.