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Importance of caveolae, cytoskeleton and dephosphoryation in glucagon receptor trafficking.
Author(s) -
Krilov Lada,
Bouscarel Bernard
Publication year - 2007
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/fasebj.21.5.a432-a
Subject(s) - internalization , caveolae , microbiology and biotechnology , filipin , receptor , cytoskeleton , chemistry , vesicle , glucagon , hek 293 cells , glucose homeostasis , biology , endocrinology , signal transduction , cell , biochemistry , insulin , membrane , insulin resistance
Glucagon regulates blood glucose homeostasis through activation of the glucagon receptor (GR). In several diseases, including Type 2 diabetes, the expression level and activity of GR are altered. The present study was conducted to elucidate the fate of internalized receptors in HEK‐293 cells stably expressing GR. METHODS: GR levels at the plasma membrane were assessed by radioligand binding using 125I‐glucagon. Interaction of FLAG‐GR with caveolin‐1 and Rab proteins was determined by fluorescence microscopy. RESULTS: GR internalization was significantly inhibited by Nystatin and Filipin, two caveolae‐disrupting agents. Colocalization of GR and caveolin‐1 was observed at 10 min of glucagon treatment. Upon glucagon removal, GR recovered on the plasma membrane within 30 min. The GR was also found associated with Rab4‐ and Rab11‐positive vesicles in the cytosolic and perimembrane domains. While inhibition of PP1 and PP2 did not affect either the internalization or recycling, disruption of actin filaments and microtubules diminished specifically GR recycling. CONCLUSIONS: In HEK‐293 cells, GR is internalized partially through a caveolin‐mediated pathway. Internalized receptors recycle through Rab4‐ and Rab11‐positive vesicles. The recycling process requires an intact cytoskeleton, but is dephosphorylation independent.