A molecular switch for coordinating kinesin and dynein transport of mitochondrial cargo
TL;DR
A regulatory helix in the mitochondrial adaptor protein (TRAK) that mediates switching between kinesin- and dynein-driven transport is identified and reveals a molecular mechanism for coordinating the directional transport of mitochondria in response to intracellular signals.
Abstract
The cellular distribution of mitochondria in response to stress and local energy needs is governed by the relative activities of the microtubule-based molecular motors kinesin and dynein. The mechanism for switching between these two opposite polarity microtubule motors remains unknown. Here, we coupled a cellular synthetic cargo transport assay with AlphaFold2-guided mutagenesis to identify a regulatory helix in the mitochondrial adaptor protein (TRAK) that mediates switching between kinesin- and dynein-driven transport. Differences in the helix sequence explained why two near-identical TRAK isoforms transported mitochondria in predominantly opposite directions. Phosphorylation of the regulatory helix by stress-activated kinases caused the activation of dynein and dissociation of kinesin. Our results reveal a molecular mechanism for coordinating the directional transport of mitochondria in response to intracellular signals.