Huntingtin S421 phosphorylation and expression levels differentially affect signalling and degradative intracellular cargoes

Abstract

Huntingtin phosphorylation and expression levels modulate endosome motility. Huntingtin acts as a scaffolding protein that recruits motor proteins to vesicular cargoes, enabling it to regulate kinesin- and dynein- dependent transport. The cell precisely regulates motor activity through post-translational modifications of scaffolding molecules including htt. We used CRISPR/Cas9 to induce a phosphomimetic mutation of the endogenous huntingtin at S421 (htt-S421D). This approach allowed us to maintain endogenous expression levels to avoid perturbing the stoichiometry of huntingtin and its many interacting partners.