Thyrotropin receptor trafficking relies on the hScrib-betaPIX-GIT1-ARF6 pathway.
G protein-coupled receptors are regulated by ligand stimulation, endocytosis, degradation of recycling to the cell surface. Little information is available on the molecular mechanisms underlying G protein-coupled receptors recycling. We have investigated recycling of the G protein-coupled thyroid stimulating hormone receptor (TSHR) and found that it relies on hScrib, a membrane-associated PDZ protein. hScrib directly binds to TSHR, inhibits basal receptor endocytosis and promotes recycling, and thus TSHR signalling, at the cell membrane. We previously demonstrated that hScrib is associated with a betaPIX-GIT1 complex comprised of a guanine nucleotide exchange factor and a GTPase-activating protein for ADP ribosylation factors that is involved in vesicle trafficking. We used dominant-negative constructs and small interfering RNA to show that TSHR recycling is regulated by the interaction between hScrib and betaPIX, and by the activity of GIT1. In addition, ARF6, a major target for GIT1, is activated during TSH stimulation of HEK293 and FRTL-5 thyroid cells, and plays a key role in TSHR recycling. Thus, we have uncovered an hScrib-betaPIX-GIT1-ARF6 pathway devoted to TSHR trafficking and function.
Lahuna
Olivier
O
INSERM E120, Récepteurs, Signalisations et Physiopathologie Thyroïdienne et de la Reproduction, Le Kremlin Bicêtre, France. olivier.lahuna@kb.inserm.fr
Quellari
Mylène
M
Achard
Caroline
C
Nola
Sébastien
S
Méduri
Géri
G
Navarro
Christel
C
Vitale
Nicolas
N
Borg
Jean-Paul
JP
Misrahi
Micheline
M
D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins / Q000378:metabolism; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D021381:Protein Transport / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D011989:Receptors, Thyrotropin / Q000378:metabolism*; D064067:Rho Guanine Nucleotide Exchange Factors; D015398:Signal Transduction / Q000502:physiology*; D025521:Tumor Suppressor Proteins; D020798:Two-Hybrid System Techniques
D000089982:ADP-Ribosylation Factor 6; D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C485647:GIT1 protein, human; D020662:Guanine Nucleotide Exchange Factors; D008565:Membrane Proteins; D010750:Phosphoproteins; D043562:Receptors, G-Protein-Coupled; D011989:Receptors, Thyrotropin; D064067:Rho Guanine Nucleotide Exchange Factors; C480591:SCRIB protein, human; D025521:Tumor Suppressor Proteins; D000242:Cyclic AMP; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human