A RILP-regulated pathway coordinating autophagosome biogenesis with transport.

Mammalian cells, including neurons, use macroautophagy (here 'autophagy') to degrade damaged proteins and organelles, and recycle nutrients in response to starvation and other forms of cell stress. The basic cellular machinery responsible for autophagy is highly conserved from yeast to mammals. However, evidence for specific adaptations to more complex organisms and in highly differentiated cells (e. g. neurons) remains limited. RILP (Rab interacting lysosomal protein) mediates retrograde transport of late endosomes (LEs) in nonneuronal mammalian cells. We have now found that RILP plays additional important, fundamental roles in neuronal autophagosome (AP) transport, and, more surprisingly, in AP biogenesis, and cargo turnover as well. RILP accomplishes these tasks via sequential interactions with key autophagosomal components - ATG5 and LC3 - as well as the microtubule motor protein cytoplasmic dynein (Figure 1A). We found further that RILP expression and behavior are controlled by MTOR kinase, linking RILP to a potentially wide range of physiological and pathophysiological functions.