Axonal transport of mitochondria requires milton to recruit kinesin heavy chain and is light chain independent

TLDR

Mitochondria are distributed within cells to meet local energy demands. Milton serves as an adaptor that recruits kinesin‑heavy chain to mitochondria, enabling light‑chain–independent anterograde transport; kinesin‑light chain antagonizes this interaction and is absent from milton–KHC complexes, while milton’s association with the GTPase miro further facilitates recruitment.

Abstract

Mitochondria are distributed within cells to match local energy demands. We report that the microtubule-dependent transport of mitochondria depends on the ability of milton to act as an adaptor protein that can recruit the heavy chain of conventional kinesin-1 (kinesin heavy chain [KHC]) to mitochondria. Biochemical and genetic evidence demonstrate that kinesin recruitment and mitochondrial transport are independent of kinesin light chain (KLC); KLC antagonizes milton's association with KHC and is absent from milton–KHC complexes, and mitochondria are present in klc −/− photoreceptor axons. The recruitment of KHC to mitochondria is, in part, determined by the NH2 terminus–splicing variant of milton. A direct interaction occurs between milton and miro, which is a mitochondrial Rho-like GTPase, and this interaction can influence the recruitment of milton to mitochondria. Thus, milton and miro are likely to form an essential protein complex that links KHC to mitochondria for light chain–independent, anterograde transport of mitochondria.