Human receptors patched and smoothened partially transduce hedgehog signal when expressed in Drosophila cells.
In humans, dysfunctions of the Hedgehog receptors Patched and Smoothened are responsible for numerous pathologies. However, signaling mechanisms involving these receptors are less well characterized in mammals than in Drosophila. To obtain structure-function relationship information on human Patched and Smoothened, we expressed these human receptors in Drosophila Schneider 2 cells. We show here that, as its Drosophila counterpart, human Patched is able to repress the signaling pathway in the absence of Hedgehog ligand. In response to Hedgehog, human Patched is able to release Drosophila Smoothened inhibition, suggesting that human Patched is expressed in a functional state in Drosophila cells. We also provide experiments showing that human Smo, when expressed in Schneider cells, is able to bind the alkaloid cyclopamine, suggesting that it is expressed in a native conformational state. Furthermore, contrary to Drosophila Smoothened, human Smoothened does not interact with the kinesin Costal 2 and thus is unable to transduce the Hedgehog signal. Moreover, cell surface fluorescent labeling suggest that human Smoothened is enriched at the Schneider 2 plasma membrane in response to Hedgehog. These results suggest that human Smoothened is expressed in a functional state in Drosophila cells, where it undergoes a regulation of its localization comparable with its Drosophila homologue. Thus, we propose that the upstream part of the Hedgehog pathway involving Hedgehog interaction with Patched, regulation of Smoothened by Patched, and Smoothened enrichment at the plasma membrane is highly conserved between Drosophila and humans; in contrast, signaling downstream of Smoothened is different.
De Rivoyre
Matthieu
M
Laboratoire de Physiologie Cellulaire et Moléculaire, CNRS Unité Mixte de Recherche (UMR) 6548, Université de Nice-Sophia Antipolis, Parc Valrose 06108 Nice Cedex 2, France.
Ruel
Laurent
L
Varjosalo
Markku
M
Loubat
Agnès
A
Bidet
Michel
M
Thérond
Pascal
P
Mus-Veteau
Isabelle
I
D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D017124:Conserved Sequence; D004330:Drosophila; D005786:Gene Expression Regulation; D053823:Hedgehog Proteins / Q000737:chemistry / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D000072079:Patched Receptors; D011487:Protein Conformation; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013045:Species Specificity
D053823:Hedgehog Proteins; D000072079:Patched Receptors; D011956:Receptors, Cell Surface