Scube/You activity mediates release of dually lipid-modified Hedgehog signal in soluble form.
Owing to their covalent modification by cholesterol and palmitate, Hedgehog (Hh) signaling proteins are localized predominantly to the plasma membrane of expressing cells. Yet Hh proteins are also capable of mobilizing to and eliciting direct responses from distant cells. The zebrafish you gene, identified genetically >15 years ago, was more recently shown to encode a secreted glycoprotein that acts cell-nonautonomously in the Hh signaling pathway by an unknown mechanism. We investigated the function of the protein encoded by murine Scube2, an ortholog of you, and found that it mediates release in soluble form of the mature, cholesterol- and palmitate-modified Sonic hedgehog protein signal (ShhNp) when added to cultured cells or purified detergent-resistant membrane microdomains containing ShhNp. The efficiency of Scube2-mediated release of ShhNp is enhanced by the palmitate adduct of ShhNp and by coexpression in ShhNp-producing cells of mDispatchedA (mDispA), a transporter-like protein with a previously defined role in the release of lipid-modified Hh signals. The structural determinants of Scube2 required for its activity in cultured cell assays match those required for rescue of you mutant zebrafish embryos, and we thus conclude that the role of Scube/You proteins in Hh signaling in vivo is to facilitate the release and mobilization of Hh proteins for distant action.
Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, California 94305, USA.
Adrian
A
Creanga
Thomas D
TD
Glenn
Randall K
RK
Mann
Adam M
AM
Saunders
William S
WS
Talbot
Philip A
PA
Beachy
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002135:Calcium-Binding Proteins; D002474:Cell-Free System; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D003470:Culture Media / Q000494:pharmacology; D003902:Detergents / Q000494:pharmacology; D057809:HEK293 Cells; D053823:Hedgehog Proteins / Q000378:metabolism*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism*; D050356:Lipid Metabolism / Q000187:drug effects; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D010168:Palmitates / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D012995:Solubility / Q000187:drug effects; D013329:Structure-Activity Relationship; D015027:Zebrafish
D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; D003470:Culture Media; D003902:Detergents; D053823:Hedgehog Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010168:Palmitates; C432427:Scube2 protein, mouse; C465570:Shh protein, mouse; C471153:dispatched protein, mouse; D002784:Cholesterol