The Hedgehog receptors PTCH1 and PTCH2 exist as active homomeric and heteromeric complexes

With the importance of Hedgehog signalling in embryonic development, tissue homeostasis and disease, understanding the molecular mechanisms of signal transduction is paramount for the design of specific, effective therapeutics. The Hedgehog receptor PTCH1 and the less studied PTCH2 isoform are evolutionarily related to bacterial RND permeases and sterol sensing proteins, which mobilise hydrophobic compounds powered by a cation gradient. Here we demonstrate that, in the active state, PTCH1 and PTCH2 form homomeric and heteromeric complexes that are inhibited by binding of Sonic Hedgehog. We show that PTCH2, unlike PTCH1, appears to have minimal cholesterol transport activity, but that conserved residues involved in cation transport are essential for its function. Heteromeric PTCH1-PTCH2 complexes depend on PTCH1’s cholesterol transport capacity, but the cation transport can be provided in trans by PTCH2, suggesting that some deleterious mutations in either isoform can be silenced by formation of heteromers, enhancing the robustness of this signal transduction system. These findings provide the molecular basis for the intriguing behaviour of PTCH2 as semi-redundant and partially overlapping in function with PTCH1 and explain the dominant negative effect of mutations that disrupt the PTCH2 cation transport triad in rare cases of cancer.

[1]  Jie Kang,et al.  Role of the hedgehog signaling pathway in rheumatic diseases: An overview , 2022, Frontiers in Immunology.

[2]  M. Sansom,et al.  Patched 1 regulates Smoothened by controlling sterol binding to its extracellular cysteine-rich domain , 2022, Science advances.

[3]  C. Siebold,et al.  Patched 1 reduces the accessibility of cholesterol in the outer leaflet of membranes , 2021, eLife.

[4]  E. Yu,et al.  Structural and Functional Diversity of Resistance-Nodulation-Cell Division Transporters. , 2020, Chemical reviews.

[5]  Marco Piñón,et al.  I Overview , 2020, The Diaries and Letters of Lord Woolton 1940-1945.

[6]  Anping Li,et al.  Hedgehog pathway activation through nanobody-mediated conformational blockade of the Patched sterol conduit , 2020, Proceedings of the National Academy of Sciences.

[7]  A. Salic,et al.  Distinct Cation Gradients Power Cholesterol Transport at Different Key Points in the Hedgehog Signaling Pathway. , 2020, Developmental cell.

[8]  Benjamin Bishop,et al.  The morphogen Sonic hedgehog inhibits its receptor Patched by a pincer grasp mechanism , 2019, Nature Chemical Biology.

[9]  A. Gerdes,et al.  A healthy individual with a homozygous PTCH2 frameshift variant: Are variants of PTCH2 associated with nevoid basal cell carcinoma syndrome? , 2019, Human Genome Variation.

[10]  J. Reiter,et al.  Misactivation of Hedgehog signaling causes inherited and sporadic cancers. , 2019, The Journal of clinical investigation.

[11]  A. Wutz,et al.  Structural basis of sterol recognition by human hedgehog receptor PTCH1 , 2018, Science Advances.

[12]  X. Gong,et al.  Inhibition of tetrameric Patched1 by Sonic Hedgehog through an asymmetric paradigm , 2018, Nature Communications.

[13]  Yifan Cheng,et al.  Structural Basis for Cholesterol Transport-like Activity of the Hedgehog Receptor Patched , 2018, Cell.

[14]  Benjamin R. Myers,et al.  Rapid, direct activity assays for Smoothened reveal Hedgehog pathway regulation by membrane cholesterol and extracellular sodium , 2017, Proceedings of the National Academy of Sciences.

[15]  A. Salic,et al.  Mechanism of inhibition of the tumor suppressor Patched by Sonic Hedgehog , 2016, Proceedings of the National Academy of Sciences.

[16]  Hang Shi,et al.  Structure of human Niemann–Pick C1 protein , 2016, Proceedings of the National Academy of Sciences.

[17]  S. Angers,et al.  Ptch2 shares overlapping functions with Ptch1 in Smo regulation and limb development. , 2015, Developmental biology.

[18]  B. Roberts,et al.  Ptch2 mediates the Shh response in Ptch1−/− cells , 2014, Development.

[19]  P. Mehlen,et al.  Patched-1 Proapoptotic Activity Is Downregulated by Modification of K1413 by the E3 Ubiquitin-Protein Ligase Itchy Homolog , 2014, Molecular and Cellular Biology.

[20]  C. Hui,et al.  Patched 1 and patched 2 redundancy has a key role in regulating epidermal differentiation. , 2014, The Journal of investigative dermatology.

[21]  D. Robbins,et al.  The Hedgehog Signal Transduction Network , 2012, Science Signaling.

[22]  H. Nikaido,et al.  Mechanisms of RND multidrug efflux pumps. , 2009, Biochimica et biophysica acta.

[23]  H. Zhang,et al.  A missense mutation in PTCH2 underlies dominantly inherited NBCCS in a Chinese family , 2008, Journal of Medical Genetics.

[24]  T. Kornberg,et al.  The C-terminal tail of the Hedgehog receptor Patched regulates both localization and turnover. , 2006, Genes & development.

[25]  Heather L. Miller,et al.  Patched2 modulates tumorigenesis in patched1 heterozygous mice. , 2006, Cancer research.

[26]  Conrad C. Huang,et al.  UCSF Chimera—A visualization system for exploratory research and analysis , 2004, J. Comput. Chem..

[27]  Dennis C. Ko,et al.  Binding between the Niemann-Pick C1 protein and a photoactivatable cholesterol analog requires a functional sterol-sensing domain. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[28]  Philip A Beachy,et al.  Novel lipid modifications of secreted protein signals. , 2004, Annual review of biochemistry.

[29]  P. Zaphiropoulos,et al.  Distinct roles of PTCH2 splice variants in Hedgehog signalling. , 2004, The Biochemical journal.

[30]  Y. Ioannou.  Niemann‐Pick C1 Protein , 2002 .

[31]  C. Tabin,et al.  Comparative biological responses to human Sonic, Indian, and Desert hedgehog , 2001, Mechanisms of Development.

[32]  M. Scott,et al.  Effects of oncogenic mutations in Smoothened and Patched can be reversed by cyclopamine , 2000, Nature.

[33]  A. Rosenthal,et al.  Characterization of two patched receptors for the vertebrate hedgehog protein family. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[34]  M. Scott,et al.  Altered neural cell fates and medulloblastoma in mouse patched mutants. , 1997, Science.