Kinesin-1 : cargo recognition and activation

• Main Author: Sanger, Anneri
• Other Authors: Steiner, Roberto ; Dodding, Mark Peter
• Published: King's College London (University of London) 2016
• Subjects: 572
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.684465

The hetrotetrameric microtubule motor protein, kinesin-1 plays a central role in the intracellular transport of protein, ribonuclear protein, vesicles and organelles on microtubules. Kinesin-1 is composed of two heavy (KHC) and two light chains (KLC). In the absence of cargo, kinesin-1 exists in an autoinhibited state where the C-terminal tail of a single heavy chain binds to the N-terminal motor domain. KLCs contribute to the maintenance of this regulated state although the mechanism is unknown. Kinesin-1 is activated upon cargo binding. Cargo have been shown to bind to the tetratricopeptide repeat (TPR) domain of KLC and the C-terminal tail of KHC. KLCs recognise a short peptide sequence present in many cargo that is characterised by a tryptophan flanked by acidic residues (Wacidic). The aim of this thesis was to further investigate these cargo recognition mechanisms with the goal of providing a framework for understanding the general principles of kinesin-1 cargo recognition and cargo dependent activation. This was pursued by attempting a detailed molecular dissection of the mechanism of recognition of lysosomal cargo adaptor SKIP which carries a pair of W-acidic motifs. In this thesis the crystal structure of the TPR domain of KLC2 in complex with a tryptophan-acidic motif derived from SKIP is presented and the key residues responsible for the interaction are identified. Further studies revealed a direct interaction between SKIP and a specific site on the Cterminal tail of KHC. Mapping of the KHC binding site on SKIP revealed both shared and distinct determinants for the KHC and KLC interaction, and binding to either may be mutually exclusive. Mutational separation of the KHC and KLC binding enabled the investigation of this novel KHC-cargo interaction in SKIP mediated cargo transport. Based on these findings a model is proposed to explain how SKIP may activate kinesin-1 to promote anterograde lysosome transport.