Functions of the SLC36 transporter Pathetic in growth control

Neurons exhibit extreme diversity in size, but whether large neurons have specialized mechanisms to support their growth is largely unknown. Recently, we identified the SLC36 transporter Pathetic (Path) as a factor required for extreme dendrite growth in neurons. Path is broadly expressed, but only neurons with large dendrite arbors or small neurons that are forced to grow large require path for their growth. To gain insight into the basis of growth control by path, we generated additional alleles of path and further examined the apparent specificity of growth defects in path mutants. Here, we confirm our prior finding that loss of path function imposes an upper limit on neuron growth, and additionally report that path likely limits overall neurite length rather than dendrite length alone. Using a GFP knock-in allele of path, we identify additional tissues where path likely functions in nutrient sensing and possibly growth control. Finally, we demonstrate that path regulates translational capacity in a cell type that does not normally require path for growth, suggesting that path may confer robustness on growth programs by buffering translational output. Altogether, these studies suggest that Path is a nutrient sensor with widespread function in Drosophila.