Autophagy receptors link myosin VI to autophagosomes to mediate Tom1-dependent autophagosome maturation and fusion with the lysosome

Abstract

Autophagy targets pathogens, damaged organelles and protein aggregates for lysosomal degradation. These ubiquitinated cargoes are recognised by specific autophagy receptors, which recruit LC3-positive membranes to form autophagosomes. Subsequently, autophagosomes fuse with endosomes and lysosomes, thus facilitating degradation of their content, however, the machinery that targets and mediates fusion of these organelles with autophagosomes remains to be established. Here we demonstrate that myosin VI, in concert with its adaptor proteins NDP52, optineurin, T6BP and Tom1, plays a crucial role in autophagy. We identify Tom1 as a myosin VI binding partner on endosomes and demonstrate that their loss reduces autophagosomal delivery of endocytic cargo and causes a block in autophagosome-lysosome fusion. We propose that myosin VI delivers endosomal membranes containing Tom1 to autophagosomes by docking to NDP52, T6BP and optineurin thereby promoting autophagosome maturation and thus driving fusion with lysosomes.

Loss of functional MYO1C/myosin 1c, a motor protein involved in lipid raft trafficking, disrupts autophagosome-lysosome fusion

“…We generated a HeLa cell line stably expressing a GFP-tagged HTT protein with a N-terminal 72 amino acid polyglutamine repeat (HTTQ72-GFP). 18 In most cells this mutant form of HTT protein is cytosolic; only a few cells (less than 20%) contained multiple HTT aggregates (>15 /cell) (Fig. 3A, B).…”

The MYO6 interactome reveals adaptor complexes coordinating early endosome and cytoskeletal dynamics

“…MYO6 CBD LI (isoform 1, Q9UM54‐1, amino acids 1037–1285) and MYO6 CBD NI (isoform 5, Q9UM54‐5, amino acids 1036–1253) WT, ΔWWY, ΔRRL and ΔPIP 2 were amplified by PCR from MYO6 FL and tail wild‐type, ΔWWY, ΔRRL and ΔPIP 2 pEGFPC constructs described elsewhere 8, 46, 47, 48 and inserted in‐frame at the 3′ end of the BirA* tag. Mammalian two‐hybrid MYO6 tail wild‐type and mutant pM constructs have been described elsewhere 9, as have GFP‐MYO6 + and GFP‐MYO10 30. HA‐MYO6 CBD was generated by PCR using primers containing the HA tag sequence.…”

“…The functional and phenotypic diversity associated with MYO6 arises from interactions with multiple cargo adaptors including disabled‐2 (DAB2), GAIP‐interacting protein C‐terminus (GIPC1), target of Myb 1 (TOM1), lemur tyrosine kinase 2 (LMTK2), optineurin (OPTN), TAX1 binding protein 1 (TAX1BP1) and nuclear dot protein 52 (NDP52) 8, 9, 10, 11, 12, 13. These interactions occur at two major protein binding motifs, the RRL and WWY (named after their amino acid composition), which are located within two distinct subdomains of a unique C‐terminal cargo‐binding tail 10, 11.…”

NDP52, autophagie et pathogènes

“…En liant la myosine VI, la seule myosine motrice permettant un mouvement rétrograde des endosomes via son interaction avec la protéine endosomale TOM-1 (target of Mybl) [12], NDP52 est physiquement associée à la voie endo-lysosomale. En liant un membre des ATG8, NDP52 connecte alors l'endosome à l'autophagosome et permet leur fusion, promouvant ainsi la maturation autophagique [11].…”