Endocytosis controller

Endocytosis and degradation of the membrane receptors in the lysosome controls the activation of intracellular signaling pathways, but the mechanisms that control the endocytosis itself are largely unknown. In January 25 Cell, Thomas Lloyd and colleagues from Baylor College of Medicine, Houston, US show that hepatocyte growth factor regulates endosome membrane invagination and tyrosine kinase receptor (TKR) signaling in Drosophila.

Lloyd et al. performed electron microscopy studies on mutant fly larvae that lacked functional Hrs and found that they had an impairment in endosome membrane invagination and formation of multivesicular bodies. In addition, hrs mutants fail to degrade active epidermal growth factor and Torso TKRs, leading to enhanced signaling and altered embryonic patterning (Cell 2002, 108:261-269).

This suggests "when Hrs attaches to the receptor and pushes it inside the vesicle, this process would end its access to the cytoplasm and thus its signaling," said Hugo...