Two Motors and One Spring: Hypothetic Roles of Non-Muscle Myosin II and Submembrane Actin-Based Cytoskeleton in Cell...

Area of Science:

• Cellular Biology
• Biophysics
• Molecular Mechanosensing

Background:

• Cell volume regulation involves changes in plasma membrane curvature and intracellular ionic strength.
• Existing models lack a comprehensive molecular apparatus for sensing these perturbations.

Purpose of the Study:

• To present a novel hypothesis for a molecular apparatus that senses plasma membrane curvature and ionic strength.
• To elucidate the role of this apparatus in activating signaling pathways for regulatory volume increase (RVI) and regulatory volume decrease (RVD).

Main Methods:

• Hypothetical modeling of a molecular apparatus comprising non-muscle myosin II (NMMII), actin polymerization, and a plasma membrane-cytoskeleton complex.
• Analysis of hydrostatic pressure (HP) driven membrane curvature changes during cell swelling and shrinkage.
• Consideration of ionic strength sensitivity of NMMII and actin cortex interactions.

Main Results:

• The proposed apparatus integrates NMMII and actin polymerization to actively probe transmembrane HP gradients.
• NMMII and actin cortex interactions are sensitive to changes in intracellular ionic strength.
• This apparatus can transduce signals from transmembrane mechanosensors to cell volume regulatory mechanisms.

Conclusions:

• A unified molecular model explains how cells sense and respond to volume changes via membrane curvature and ionic strength.
• Non-muscle myosin II and actin dynamics are central to this mechanosensing and regulatory process.
• This hypothesis provides a framework for future experimental validation of cell volume control mechanisms.