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An epidermal growth factor (EGF) ‐dependent interaction between GIT1 and sorting nexin 6 promotes degradation of the EGF receptor
Author(s) -
Cavet Megan E.,
Pang Jinjiang,
Yin Guoyong,
Berk Bradford C.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.07-094086
Subject(s) - endosome , epidermal growth factor receptor , epidermal growth factor , sorting nexin , biology , scaffold protein , small interfering rna , receptor tyrosine kinase , microbiology and biotechnology , gefitinib , tyrosine kinase , erbb3 , phosphorylation , cancer research , signal transduction , receptor , cell culture , biochemistry , transfection , intracellular , genetics
G‐protein coupled receptor (GPCR) ki‐nase‐2 interacting protein 1 (GIT1) is a multifunctional scaffolding protein that regulates epidermal growth factor receptor (EGFR) signaling pathways. We demonstrate that GIT1 interacts with sorting nexin 6 (SNX6), a member of the SNX family that increases EGFR trafficking between endosomes and lysosomes, thereby enhancing EGFR degradation. The GIT1‐SNX6 interaction is increased 3‐fold after treatment with EGF for 60 min. The second coiled‐coil domain (CC2;aa 424–474) of GIT1 mediates binding to SNX6. Subcellular fractionation and confocal microscopy data indicate that GIT1 and SNX6 interact in endosomes. Knockdown of GIT1 expression by small interfering RNA decreased the rate of EGF‐induced EGFR degradation. Expression of exogenous GIT1 or SNX6 alone did not alter EGFR degradation;however, coexpression of GIT1 and SNX6 decreased EGFR levels both basally and in response to EGF. In contrast, expression of GIT1(CC2 deleted) and SNX6 did not reduce EGFR levels, demonstrating that the interaction between GIT1 and SNX6 was required to regulate EGFR trafficking. Phosphorylation of the EGFR substrate phospholipase C‐γ was decreased by coexpression of GIT1 and SNX6. These data demonstrate an endosomal, EGF‐regulated interaction between SNX6 and GIT1 that enhances degradation of the EGFR, and thereby alters EGFR signaling. Our findings suggest a new role for GIT1 in tyrosine kinase receptor trafficking.—Cavet, M. E., Pang, J., Yin, G., Berk, B. C. An epidermal growth factor (EGF) ‐dependent interaction between GIT1 and sorting nexin 6 promotes degradation of the EGF receptor. FASEB J. 22, 3607–3616 (2008)