title: An emerging role of Sonic hedgehog shedding as a modulator of heparan sulfate interactions.
abstract: Major developmental morphogens of the Hedgehog (Hh) family act at short range and long range to direct cell fate decisions in vertebrate and invertebrate tissues. To this end, Hhs are released from local sources and act at a distance on target cells that express the Hh receptor Patched. However, morphogen secretion and spreading are not passive processes because all Hhs are synthesized as dually (N- and C-terminal) lipidated proteins that firmly tether to the surface of producing cells. On the cell surface, Hhs associate with each other and with heparan sulfate (HS) proteoglycans. This raises the question of how Hh solubilization and spreading is achieved. We recently discovered that Sonic hedgehog (Shh) is solubilized by proteolytic processing (shedding) of lipidated peptide termini in vitro. Because unprocessed N termini block Patched receptor binding sites in the cluster, we further suggested that their proteolytic removal is required for simultaneous Shh activation. In this work we confirm inactivity of unprocessed protein clusters and demonstrate restored biological Shh function upon distortion or removal of N-terminal amino acids and peptides. We further show that N-terminal Shh processing targets and inactivates the HS binding Cardin-Weintraub (CW) motif, resulting in soluble Shh clusters with their HS binding capacities strongly reduced. This may explain the ability of Shh to diffuse through the HS-containing extracellular matrix, whereas other HS-binding proteins are quickly immobilized. Our in vitro findings are supported by the presence of CW-processed Shh in murine brain samples, providing the first in vivo evidence for Shh shedding and subsequent solubilization of N-terminal-truncated proteins.
authors.affiliation: Institute for Physiological Chemistry and Pathobiochemistry, University Hospital Münster, Waldeyerstrasse 15, D-48149 Münster, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Ohlig
authors.forename: Ute
authors.initials: U
authors.lastname: Pickhinke
authors.forename: Svetlana
authors.initials: S
authors.lastname: Sirko
authors.forename: Shyam
authors.initials: S
authors.lastname: Bandari
authors.forename: Daniel
authors.initials: D
authors.lastname: Hoffmann
authors.forename: Rita
authors.initials: R
authors.lastname: Dreier
authors.forename: Pershang
authors.initials: P
authors.lastname: Farshi
authors.forename: Magdalena
authors.initials: M
authors.lastname: Götz
authors.forename: Kay
authors.initials: K
authors.lastname: Grobe
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D002460:Cell Line; D005109:Extracellular Matrix / Q000235:genetics / Q000378:metabolism*; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D006497:Heparan Sulfate / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D054878:Lipoylation / Q000502:physiology; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D000072079:Patched Receptors; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism
chemical_list: D053823:Hedgehog Proteins; D006497:Heparan Sulfate; D009419:Nerve Tissue Proteins; D000072079:Patched Receptors; D011956:Receptors, Cell Surface; C465570:Shh protein, mouse