scholarly journals Cholesterol accessibility at the ciliary membrane controls hedgehog signaling

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Maia Kinnebrew ◽  
Ellen J Iverson ◽  
Bhaven B Patel ◽  
Ganesh V Pusapati ◽  
Jennifer H Kong ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Birth Defects ◽  
Hedgehog Signaling ◽  
Signal Transmission ◽  
Membrane Cholesterol ◽  
Signaling Proteins ◽  
Signaling System ◽  
Ciliary Membrane ◽  
Patched 1 ◽  
Hedgehog Signal

Previously we proposed that transmission of the hedgehog signal across the plasma membrane by Smoothened is triggered by its interaction with cholesterol (Luchetti et al., 2016). But how is cholesterol, an abundant lipid, regulated tightly enough to control a signaling system that can cause birth defects and cancer? Using toxin-based sensors that distinguish between distinct pools of cholesterol, we find that Smoothened activation and hedgehog signaling are driven by a biochemically-defined, small fraction of membrane cholesterol, termed accessible cholesterol. Increasing cholesterol accessibility by depletion of sphingomyelin, which sequesters cholesterol in complexes, amplifies hedgehog signaling. Hedgehog ligands increase cholesterol accessibility in the membrane of the primary cilium by inactivating the transporter-like protein Patched 1. Trapping this accessible cholesterol blocks hedgehog signal transmission across the membrane. Our work shows that the organization of cholesterol in the ciliary membrane can be modified by extracellular ligands to control the activity of cilia-localized signaling proteins.

scholarly journals Sphingomyelin suppresses Hedgehog signaling by restricting cholesterol accessibility at the ciliary membrane

2019 ◽  
Author(s):  
Maia Kinnebrew ◽  
Ellen J. Iverson ◽  
Bhaven B. Patel ◽  
Ganesh V. Pusapati ◽  
Jennifer H. Kong ◽  
...  
Keyword(s):  
Hedgehog Signaling ◽  
Direct Interaction ◽  
Subcellular Location ◽  
Signaling System ◽  
Ciliary Membrane ◽  
Cellular Processes ◽  
Cholesterol Levels ◽  
Collateral Effects ◽  
Patched 1 ◽  
Hedgehog Signal

AbstractTransmission of the Hedgehog signal across the plasma membrane by Smoothened is proposed to be triggered by its direct interaction with cholesterol. But how is cholesterol, an abundant lipid, regulated tightly enough to control a signaling system that can cause birth defects and cancer? Using toxin-based sensors that distinguish between distinct pools of cholesterol, we find here that Smoothened activation and Hedgehog signaling are driven by a biochemically defined fraction of membrane cholesterol, termed accessible cholesterol. Increasing accessible cholesterol levels by depletion of sphingomyelin, which sequesters cholesterol in complexes, potentiates Hedgehog signaling. By inactivating the transporter-like protein Patched 1, Hedgehog ligands trigger an increase in cholesterol accessibility in the ciliary membrane, the subcellular location for Smoothened signaling. Thus, compartmentalization of Hedgehog signaling in the primary cilium may allow cholesterol accessibility to be used as a second messenger to mediate the communication between Patched 1 and Smoothened, without causing collateral effects on other cellular processes.

scholarly journals Lateral transport of Smoothened from the plasma membrane to the membrane of the cilium

2009 ◽  
Vol 187 (3) ◽  
pp. 365-374 ◽  
Author(s):  
Ljiljana Milenkovic ◽  
Matthew P. Scott ◽  
Rajat Rohatgi
Keyword(s):  
Plasma Membrane ◽  
Protein Trafficking ◽  
Primary Cilia ◽  
Protein Transport ◽  
Transmembrane Protein ◽  
Signaling Proteins ◽  
Lateral Transport ◽  
Transport Pathway ◽  
Ciliary Membrane ◽  
Specific Proteins

The function of primary cilia depends critically on the localization of specific proteins in the ciliary membrane. A major challenge in the field is to understand protein trafficking to cilia. The Hedgehog (Hh) pathway protein Smoothened (Smo), a 7-pass transmembrane protein, moves to cilia when a ligand is received. Using microscopy-based pulse-chase analysis, we find that Smo moves through a lateral transport pathway from the plasma membrane to the ciliary membrane. Lateral movement, either via diffusion or active transport, is quite distinct from currently studied pathways of ciliary protein transport in mammals, which emphasize directed trafficking of Golgi-derived vesicles to the base of the cilium. We anticipate that this alternative route will be used by other signaling proteins that function at cilia. The path taken by Smo may allow novel strategies for modulation of Hh signaling in cancer and regeneration.

scholarly journals Patched 1 reduces the accessibility of cholesterol in the outer leaflet of membranes

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Maia Kinnebrew ◽  
Giovanni Luchetti ◽  
Ria Sircar ◽  
Sara Frigui ◽  
Lucrezia Vittoria Viti ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Sonic Hedgehog ◽  
Hedgehog Signaling ◽  
Live Cells ◽  
Transport Activity ◽  
Outer Leaflet ◽  
Cholesterol Levels ◽  
Patched 1 ◽  
Potassium Gradient ◽  
Kinetics Of

A long-standing mystery in vertebrate Hedgehog signaling is how Patched 1 (PTCH1), the receptor for Hedgehog ligands, inhibits the activity of Smoothened, the protein that transmits the signal across the membrane. We previously proposed (Kinnebrew et al., 2019) that PTCH1 inhibits Smoothened by depleting accessible cholesterol from the ciliary membrane. To directly test the effect of PTCH1 on accessible cholesterol, we measured the transport activity of PTCH1 using an imaging-based assay to follow the kinetics of cholesterol extraction from the plasma membrane of live cells by methyl-β-cyclodextrin. PTCH1 depletes accessible cholesterol in the outer leaflet of the membrane in a manner regulated by its ligand Sonic Hedgehog and the transmembrane potassium gradient. We propose that PTCH1 moves cholesterol from the outer to the inner leaflet of the membrane in exchange for potassium ion export. Our results show that proteins can change accessible cholesterol levels in membranes to regulate signaling reaction.

scholarly journals Sterols, Oxysterols, and Accessible Cholesterol: Signalling for Homeostasis, in Immunity and During Development

2021 ◽  
Vol 12 ◽  
Author(s):  
William J. Griffiths ◽  
Yuqin Wang
Keyword(s):  
Plasma Membrane ◽  
Total Cell ◽  
Cholesterol Homeostasis ◽  
Microbial Pathogens ◽  
Membrane Cholesterol ◽  
Hedgehog Signalling ◽  
Signalling Molecule ◽  
Hedgehog Signalling Pathway ◽  
Patched 1 ◽  
Plasma Membrane Cholesterol

In this article we discuss the concept of accessible plasma membrane cholesterol and its involvement as a signalling molecule. Changes in plasma membrane accessible cholesterol, although only being minor in the context of total cholesterol plasma membrane cholesterol and total cell cholesterol, are a key regulator of overall cellular cholesterol homeostasis by the SREBP pathway. Accessible cholesterol also provides the second messenger between patched 1 and smoothened in the hedgehog signalling pathway important during development, and its depletion may provide a mechanism of resistance to microbial pathogens including SARS-CoV-2. We revise the hypothesis that oxysterols are a signalling form of cholesterol, in this instance as a rapidly acting and paracrine version of accessible cholesterol.

scholarly journals Monoclonal antibody detection of plasma membrane cholesterol microdomains responsive to cholesterol trafficking

2001 ◽  
Vol 42 (9) ◽  
pp. 1492-1500 ◽  
Author(s):  
Howard S. Kruth ◽  
Ina Ifrim ◽  
Janet Chang ◽  
Lia Addadi ◽  
Daniele Perl-Treves ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Plasma Membrane ◽  
Antibody Detection ◽  
Membrane Cholesterol ◽  
Cholesterol Trafficking ◽  
Plasma Membrane Cholesterol

Cell culturing in a three-dimensional matrix affects the localization and properties of plasma membrane cholesterol

2009 ◽  
Vol 33 (10) ◽  
pp. 1079-1086 ◽  
Author(s):  
Nadezhda Stefanova ◽  
Galya Staneva ◽  
Diana Petkova ◽  
Teodora Lupanova ◽  
Roumen Pankov ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Three Dimensional ◽  
Membrane Cholesterol ◽  
Dimensional Matrix ◽  
Cell Culturing ◽  
Plasma Membrane Cholesterol

scholarly journals Trafficking to the primary cilium membrane

2017 ◽  
Vol 28 (2) ◽  
pp. 233-239 ◽  
Author(s):  
Saikat Mukhopadhyay ◽  
Hemant B. Badgandi ◽  
Sun-hee Hwang ◽  
Bandarigoda Somatilaka ◽  
Issei S. Shimada ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Signaling Pathways ◽  
Primary Cilium ◽  
Hedgehog Signaling ◽  
Diffusion Barriers ◽  
Disease Pathogenesis ◽  
Ciliary Membrane ◽  
Multiple Organs ◽  
Sensory Reception

The primary cilium has been found to be associated with a number of cellular signaling pathways, such as vertebrate hedgehog signaling, and implicated in the pathogenesis of diseases affecting multiple organs, including the neural tube, kidney, and brain. The primary cilium is the site where a subset of the cell's membrane proteins is enriched. However, pathways that target and concentrate membrane proteins in cilia are not well understood. Processes determining the level of proteins in the ciliary membrane include entry into the compartment, removal, and retention by diffusion barriers such as the transition zone. Proteins that are concentrated in the ciliary membrane are also localized to other cellular sites. Thus it is critical to determine the particular role for ciliary compartmentalization in sensory reception and signaling pathways. Here we provide a brief overview of our current understanding of compartmentalization of proteins in the ciliary membrane and the dynamics of trafficking into and out of the cilium. We also discuss major unanswered questions regarding the role that defects in ciliary compartmentalization might play in disease pathogenesis. Understanding the trafficking mechanisms that underlie the role of ciliary compartmentalization in signaling might provide unique approaches for intervention in progressive ciliopathies.

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