APC couples neuronal mRNAs to multiple kinesins, EB1 and shrinking microtubule ends for bidirectional mRNA motility

Abstract

Understanding where in the cytoplasm mRNAs are translated is increasingly recognised as being as important as knowing the timing and level of protein expression. mRNAs are localised via active motor-driven transport along microtubules (MTs) but the underlying essential factors and dynamic interactions are largely unknown. Using biochemical in vitro reconstitutions with purified mammalian proteins, multi-colour TIRF-microscopy (TIRF-M), and interaction kinetics measurements, we show that adenomatous polyposis coli (APC) enables kinesin-1- and kinesin-2-based mRNA transport, and that APC is an ideal adaptor for long-range mRNA transport as it forms highly stable complexes with 3’UTR fragments of several neuronal mRNAs (APC-RNPs). The kinesin-1 KIF5A binds and transports several neuronal mRNP components such as FMRP, PUR and mRNA fragments weakly, whereas the transport frequency of the mRNA fragments is significantly increased by APC. APC-RNP-motor complexes can assemble on MTs, generating highly processive mRNA transport events.