Puschmann, J. | Search bioRxiv

bioRxiv2025

Scube2 primes Dispatched and ADAM10-mediated Shh release by recruiting HDL acceptors to the plasma membrane

Sonic hedgehog (Shh) morphogens are lipidated proteins that firmly attach to the outer plasma membrane (PM) of the cells that produce them. The process by which Shh is solubilized includes the transmembrane protein Dispatched1 (Disp), the soluble glycoprotein Scube2, the proteolytic removal of lipidated peptide termini, and the use of soluble lipoproteins (LPPs) as Shh transporters. However, their molecular interplay remains controversial. Here, we demonstrate that A Disintegrin and Metalloproteinase 10, Scube2, and Disp act synergistically to remove Shh from the PM and transfer it to LPP acceptors. We also demonstrate physical Scube2 interactions with LPPs and that these interactions increase Shh release. Finally, we demonstrate that Scube2 strongly binds to heparan sulfate (HS) on cell surfaces. These findings reveal Scube2s previously unknown role in binding low-abundance, soluble LPP carriers for Shh and recruiting these carriers to HS-rich Shh release sites at the PM to enhance morphogen release.

cell biology↗

bioRxiv2023

Two-way Dispatched function in Sonic hedgehog shedding and transfer to high-density lipoproteins

The Sonic hedgehog (Shh) signaling pathway controls embryonic development and tissue homeostasis after birth. This requires regulated solubilization of dual-lipidated, firmly plasma membrane-associated Shh precursors from producing cells. Although it is firmly established that the resistance-nodulation-division transporter Dispatched (Disp) drives this process, it is less clear how lipidated Shh solubilization from the plasma membrane is achieved. We have previously shown that Disp promotes proteolytic solubilization of Shh from its lipidated terminal peptide anchors. This process, termed shedding, converts tightly membrane-associated hydrophobic Shh precursors into delipidated soluble proteins. We show here that Disp-mediated Shh shedding is modulated by a serum factor that we identify as high-density lipoprotein (HDL). In addition to serving as a soluble sink for free membrane cholesterol, HDLs also accept the cholesterol-modified Shh peptide from Disp. The cholesteroylated Shh peptide is necessary and sufficient for Disp-mediated transfer because artificially cholesteroylated mCherry associates with HDL in a Disp-dependent manner, whereas an N-palmitoylated Shh variant lacking C- cholesterol does not. Disp-mediated Shh transfer to HDL is completed by proteolytic processing of the palmitoylated N-terminal membrane anchor. In contrast to dual processed soluble Shh with moderate bioactivity, HDL-associated N-processed Shh is highly bioactive. We propose that the purpose of generating different soluble forms of Shh from the dual lipidated precursor is to tune cellular responses in a tissue-type and time-specific manner.

cell biology↗