The G-protein coupled receptor associated sorting protein GASP-1 regulates the signalling and trafficking of the viral chemokine receptor US28.
Human cytomegalovirus (HCMV) encodes the seven transmembrane(7TM)/G-protein coupled receptor (GPCR) US28, which signals and endocytoses in a constitutive, ligand-independent manner. Here we show that, following endocytosis, US28 is targeted to the lysosomes for degradation as a consequence of its interaction with the GPCR-associated sorting protein-1 (GASP-1). We find that GASP-1 binds to US28 in vitro and that disruption of the GASP-1/US28 interaction by either (i) overexpression of dominant negative cGASP-1 or by (ii) shRNA knock-down of endogenous GASP-1 is sufficient to inhibit the lysosomal targeting of US28 and slow its post-endocytic degradation. Furthermore, we found that GASP-1 affects US28-mediated signalling. The knock-down of endogenous GASP-1 impairs the US28-mediated Galphaq/PLC/inositol phosphate (IP) accumulation as well as the activation of the transcription factors Nuclear Factor-kappaB (NF-kappaB) and cyclic AMP responsive element binding protein (CREB). Overexpression of GASP-1 enhances both IP accumulation and transcription factor activity. Thus, GASP-1 is an important cellular determinant that not only regulates the post-endocytic trafficking of US28, but also regulates the signalling capacities of US28.
Tschische
Pia
P
Institute for Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria.
Moser
Elisabeth
E
Thompson
Dawn
D
Vischer
Henry F
HF
Parzmair
Gerald P
GP
Pommer
Veronika
V
Platzer
Wolfgang
W
Schwarzbraun
Thomas
T
Schaider
Helmut
H
Smit
Martine J
MJ
Martini
Lene
L
Whistler
Jennifer L
JL
Waldhoer
Maria
M
D018925:Chemokines / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D003587:Cytomegalovirus / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D008024:Ligands; D016328:NF-kappa B / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D019707:Receptors, Chemokine / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism
D018925:Chemokines; D017362:Cyclic AMP Response Element-Binding Protein; D007295:Inositol Phosphates; D008024:Ligands; D016328:NF-kappa B; D011506:Proteins; D019707:Receptors, Chemokine; D043562:Receptors, G-Protein-Coupled; D010738:Type C Phospholipases