Antenna mechanism of length control of actin cables

TL;DR

This paper proposes a novel molecular 'antenna' mechanism involving formins, Smy1 proteins, and myosin motors that regulates actin cable length in cells, supported by computational modeling and testable predictions.

Contribution

It introduces a new molecular mechanism for actin cable length control based on recent experimental observations, with a computational model predicting length distributions.

Findings

Probability distribution of cable lengths derived

Dependence on formin-binding affinity and myosin concentration shown

Testable predictions for experimental validation provided

Abstract

Actin cables are linear cytoskeletal structures that serve as tracks for myosin-based intracellular transport of vesicles and organelles in both yeast and mammalian cells. In a yeast cell undergoing budding, cables are in constant dynamic turnover yet some cables grow from the bud neck toward the back of the mother cell until their length roughly equals the diameter of the mother cell. This raises the question: how is the length of these cables controlled? Here we describe a novel molecular mechanism for cable length control inspired by recent experimental observations in cells. This antenna mechanism involves three key proteins: formins, which polymerize actin, Smy1 proteins, which bind formins and inhibit actin polymerization, and myosin motors, which deliver Smy1 to formins, leading to a length-dependent actin polymerization rate. We compute the probability distribution of cable lengths as a function of several experimentally tuneable parameters such as the formin-binding affinity of Smy1 and the concentration of myosin motors delivering Smy1. These results provide testable predictions of the antenna mechanism of actin-cable length control.