First published online November 8, 2006
Journal of Cell Science 119, 2205e (2006)
© The Company of Biologists Limited
GRIFter implicated in receptor trafficking
Endosome-to-lysosome trafficking of internalized cell-surface receptors is critical for the control of cell signalling. However, the molecular mechanisms that control endosomal sorting are poorly understood. On p. 4689, Lian Li and colleagues identify GRIF1
-amino-n-butyric acid A (GABAA) receptor interacting factor 1 as a new regulator of this process. A key protein in the control of endosomal trafficking is hepatocyte-growth-factor-regulated tyrosine kinase substrate (Hrs). To understand more about this protein's function, the authors used yeast two-hybrid screening to identify its binding partners. They report that GRIF1 interacts with Hrs and that the two proteins colocalize on early endosomes. Overexpression of GRIF1 and knocking it down by RNAi both inhibit the degradation of internalized epidermal growth factor receptors by blocking their trafficking from endosomes to lysosomes. Interestingly, the authors find that GRIF1 also regulates the movement of early endosomes along microtubules through its interaction with the kinesin motor protein. They suggest, therefore, that GRIF1 modulates endosome transport by acting as an adaptor protein that links Hrs-containing early endosomes to kinesin.

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Related articles in JCS:
- GRIF1 binds Hrs and is a new regulator of endosomal trafficking
- Elizabeth Kirk, Lih-Shen Chin, and Lian Li
JCS 2006 119: 4689-4701.
[Abstract]
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