scholarly journals Hedgehog-Interacting Protein is a multimodal antagonist of Hedgehog signalling

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Samuel C. Griffiths ◽  
Rebekka A. Schwab ◽  
Kamel El Omari ◽  
Benjamin Bishop ◽  
Ellen J. Iverson ◽  
...  
Keyword(s):  
Cell Surface ◽  
Sonic Hedgehog ◽  
High Avidity ◽  
Interacting Protein ◽  
Surface Receptors ◽  
Terminal Domain ◽  
Inhibitory Function ◽  
Rich Domain ◽  
Covalently Linked ◽  
Cysteine Rich Domain

AbstractHedgehog (HH) morphogen signalling, crucial for cell growth and tissue patterning in animals, is initiated by the binding of dually lipidated HH ligands to cell surface receptors. Hedgehog-Interacting Protein (HHIP), the only reported secreted inhibitor of Sonic Hedgehog (SHH) signalling, binds directly to SHH with high nanomolar affinity, sequestering SHH. Here, we report the structure of the HHIP N-terminal domain (HHIP-N) in complex with a glycosaminoglycan (GAG). HHIP-N displays a unique bipartite fold with a GAG-binding domain alongside a Cysteine Rich Domain (CRD). We show that HHIP-N is required to convey full HHIP inhibitory function, likely by interacting with the cholesterol moiety covalently linked to HH ligands, thereby preventing this SHH-attached cholesterol from binding to the HH receptor Patched (PTCH1). We also present the structure of the HHIP C-terminal domain in complex with the GAG heparin. Heparin can bind to both HHIP-N and HHIP-C, thereby inducing clustering at the cell surface and generating a high-avidity platform for SHH sequestration and inhibition. Our data suggest a multimodal mechanism, in which HHIP can bind two specific sites on the SHH morphogen, alongside multiple GAG interactions, to inhibit SHH signalling.

scholarly journals The Cysteine-rich Domain of the Secreted Proprotein Convertases PC5A and PACE4 Functions as a Cell Surface Anchor and Interacts with Tissue Inhibitors of Metalloproteinases

2005 ◽  
Vol 16 (11) ◽  
pp. 5215-5226 ◽  
Author(s):  
Nadia Nour ◽  
Gaétan Mayer ◽  
John S. Mort ◽  
Alexandre Salvas ◽  
Majambu Mbikay ◽  
...  
Keyword(s):  
Cell Surface ◽  
Tissue Inhibitors Of Metalloproteinases ◽  
Endothelial Lipase ◽  
Proprotein Convertases ◽  
Tissue Inhibitors ◽  
Rich Domain ◽  
Liver Sinusoids ◽  
A Cell ◽  
Biochemical Analyses ◽  
Cysteine Rich Domain

The proprotein convertases PC5, PACE4 and furin contain a C-terminal cysteine-rich domain (CRD) of unknown function. We demonstrate that the CRD confers to PC5A and PACE4 properties to bind tissue inhibitors of metalloproteinases (TIMPs) and the cell surface. Confocal microscopy and biochemical analyses revealed that the CRD is essential for cell surface tethering of PC5A and PACE4 and that it colocalizes and coimmunoprecipitates with the full-length and C-terminal domain of TIMP-2. Surface-bound PC5A in TIMP-2 null fibroblasts was only observed upon coexpression with TIMP-2. In COS-1 cells, plasma membrane-associated PC5A can be displaced by heparin, suramin, or heparinases I and III and by competition with excess exogenous TIMP-2. Furthermore, PC5A and TIMP-2 are shown to be colocalized over the surface of enterocytes in the mouse duodenum and jejunum, as well as in liver sinusoids. In conclusion, the CRD of PC5A and PACE4 functions as a cell surface anchor favoring the processing of their cognate surface-anchored substrates, including endothelial lipase.

scholarly journals Cholesterol activates the G-protein coupled receptor Smoothened to promote morphogenetic signaling

2016 ◽  
Author(s):  
Giovanni Luchetti ◽  
Ria Sircar ◽  
Jennifer H. Kong ◽  
Sigrid Nachtergaele ◽  
Andreas Sagner ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Cell Surface ◽  
G Protein ◽  
Cell Communication ◽  
G Protein Coupled Receptors ◽  
Rich Domain ◽  
Hh Signaling ◽  
G Protein Coupled ◽  
Orphan Gpcr ◽  
Cysteine Rich Domain

AbstractCholesterol is necessary for the function of many G-protein coupled receptors (GPCRs). We find that cholesterol is not just necessary but also sufficient to activate signaling by the Hedgehog (Hh) pathway, a prominent cell-cell communication system in development. Cholesterol influences Hh signaling by directly activating Smoothened (SMO), an orphan GPCR that transmits the Hh signal across the membrane in all animals. Unlike most GPCRs, which are regulated by cholesterol through their heptahelical transmembrane domains, SMO is activated by cholesterol through its extracellular cysteine-rich domain (CRD). Residues shown to mediate cholesterol binding to the CRD in a recent structural analysis also dictate SMO activation, both in response to cholesterol and to native Hh ligands. Our results show that cholesterol can initiate signaling from the cell surface by engaging the extracellular domain of a GPCR and suggest that SMO activity may be regulated by local changes in cholesterol abundance or accessibility.

scholarly journals Gain-of-function Shh mutants activate Smo in cis independent of Ptch1/2 function

2017 ◽  
Author(s):  
Catalina Casillas ◽  
Henk Roelink
Keyword(s):  
Sonic Hedgehog ◽  
Gain Of Function ◽  
Shh Signaling ◽  
Rich Domain ◽  
Intrinsic Mechanism ◽  
Cell Autonomy ◽  
Catalytic Motif ◽  
In Cis ◽  
Cysteine Rich Domain

AbstractSonic Hedgehog (Shh) signaling is characterized by strict non-cell autonomy; cells expressing Shh do not respond to their ligand. Here, we identify several Shh mutations that gain the ability to activate the Hedgehog (Hh) pathway in cis. This activation requires the extracellular cysteine rich domain of Smoothened, but is otherwise independent of Ptch1/2. Many of the identified mutations disrupt either a highly conserved catalytic motif found in peptidases or an a-helix domain frequently mutated in holoprosencephaly-causing SHH alleles. The expression of gain-of-function mutants often results in the accumulation of unprocessed Shh pro-peptide, a form of Shh we demonstrate is sufficient to activate the Hh response cell-autonomously. Our results demonstrate that Shh is capable of activating the Hh pathway via Smo independently of Ptch1/2, and that it harbors an intrinsic mechanism that prevents cell-autonomous activation of the pathway to favor non-cell autonomous signaling.

Endogenous thrombospondin-1 is a cell-surface ligand for regulation of integrin-dependent T-lymphocyte adhesion

Blood ◽  
2006 ◽  
Vol 108 (9) ◽  
pp. 3112-3120 ◽  
Author(s):  
Shu Shun Li ◽  
Zhiwen Liu ◽  
Mehmet Uzunel ◽  
Karl-Gösta Sundqvist
Keyword(s):  
T Cell ◽  
Cell Surface ◽  
Surface Expression ◽  
Lymphocyte Adhesion ◽  
Surface Receptors ◽  
Terminal Domain ◽  
Thrombospondin 1 ◽  
A Cell ◽  
Surface Ligand ◽  
Quiescent T Cells

Abstract Lymphocyte adhesion to cells and extracellular matrix (ECM) via integrins plays a pivotal role for the function of the immune system. We show here that endogenous thrombospondin-1 (TSP-1) is a cell-surface ligand for cis interaction of surface receptors in T lymphocytes controlled by integrins and the T-cell antigen receptor (TCR/CD3). Stimulation of CD3 triggers rapid surface expression of TSP-1 in quiescent T cells, whereas activated cells express TSP-1 constitutively. Endogenous TSP-1 is attached to lipoprotein receptor-related protein 1 (LRP1/CD91) and calreticulin (CRT) on the cell surface through its NH2-terminal domain. Adhesion via integrins to ICAM-1 or ECM components up-regulates TSP turnover dramatically from a low level in nonadherent cells, whereas CD3 stimulation inhibits TSP turnover through interference with CD91/CRT-mediated internalization. Integrin-associated protein (IAP/CD47) is essential for TSP turnover and adhesion through interaction with the C-terminal domain of TSP-1 in response to triggering signals delivered at the NH2-terminal. These results indicate that endogenous TSP-1 connects separate cell-surface receptors functionally and regulates T-cell adhesion.

scholarly journals The cysteine-rich domain regulates ADAM protease function in vivo

2002 ◽  
Vol 159 (5) ◽  
pp. 893-902 ◽  
Author(s):  
Katherine M. Smith ◽  
Alban Gaultier ◽  
Helene Cousin ◽  
Dominique Alfandari ◽  
Judith M. White ◽  
...  
Keyword(s):  
Cell Surface ◽  
Xenopus Laevis ◽  
Essential Role ◽  
Active Role ◽  
Cement Gland ◽  
Cell Behavior ◽  
Rich Domain ◽  
Disintegrin Domain ◽  
Cysteine Rich Domain

ADAMs are membrane-anchored proteases that regulate cell behavior by proteolytically modifying the cell surface and ECM. Like other membrane-anchored proteases, ADAMs contain candidate “adhesive” domains downstream of their metalloprotease domains. The mechanism by which membrane-anchored cell surface proteases utilize these putative adhesive domains to regulate protease function in vivo is not well understood. We address this important question by analyzing the relative contributions of downstream extracellular domains (disintegrin, cysteine rich, and EGF-like repeat) of the ADAM13 metalloprotease during Xenopus laevis development. When expressed in embryos, ADAM13 induces hyperplasia of the cement gland, whereas ADAM10 does not. Using chimeric constructs, we find that the metalloprotease domain of ADAM10 can substitute for that of ADAM13, but that specificity for cement gland expansion requires a downstream extracellular domain of ADAM13. Analysis of finer resolution chimeras indicates an essential role for the cysteine-rich domain and a supporting role for the disintegrin domain. These and other results reveal that the cysteine-rich domain of ADAM13 cooperates intramolecularly with the ADAM13 metalloprotease domain to regulate its function in vivo. Our findings thus provide the first evidence that a downstream extracellular adhesive domain plays an active role in regulating ADAM protease function in vivo. These findings are likely relevant to other membrane-anchored cell surface proteases.

scholarly journals Insulin’s Discovery: New Insights on Its Hundredth Birthday: From Insulin Action and Clearance to Sweet Networks

2021 ◽  
Vol 22 (3) ◽  
pp. 1030
Author(s):  
Melanie Leroux ◽  
Martial Boutchueng-Djidjou ◽  
Robert Faure
Keyword(s):  
Type 1 Diabetes ◽  
Cell Surface ◽  
20Th Century ◽  
Insulin Action ◽  
100Th Anniversary ◽  
The Body ◽  
Nobel Lecture ◽  
Surface Receptors ◽  
The Third

In 2021, the 100th anniversary of the isolation of insulin and the rescue of a child with type 1 diabetes from death will be marked. In this review, we highlight advances since the ingenious work of the four discoverers, Frederick Grant Banting, John James Rickard Macleod, James Bertram Collip and Charles Herbert Best. Macleoad closed his Nobel Lecture speech by raising the question of the mechanism of insulin action in the body. This challenge attracted many investigators, and the question remained unanswered until the third part of the 20th century. We summarize what has been learned, from the discovery of cell surface receptors, insulin action, and clearance, to network and precision medicine.

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