Structural Basis Identified for Cholesterol Transport-Like Activity of the Hedgehog Receptor Patched: New evidence suggests that the Hedgehog receptor Patched may mediate cholesterol removal from the inner leaflet of the plasma membrane using a hydrophobi

2019 ◽  
Vol 179 (4) ◽  
pp. 518-519
Keyword(s):  
Plasma Membrane ◽  
Structural Basis ◽  
Cholesterol Transport ◽  
Cholesterol Removal ◽  
New Evidence

scholarly journals Structural basis for cholesterol transport-like activity of the Hedgehog receptor Patched

2018 ◽  
Author(s):  
Yunxiao Zhang ◽  
David P. Bulkley ◽  
Kelsey J. Roberts ◽  
Yao Xin ◽  
Daniel E. Asarnow ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Basal Cell Carcinoma ◽  
Cell Carcinoma ◽  
Transmembrane Domain ◽  
Transmembrane Protein ◽  
Extracellular Domain ◽  
Structural Basis ◽  
Cholesterol Transport ◽  
Common Cause ◽  
Common Receptor

AbstractHedgehog protein signals mediate tissue patterning and maintenance via binding to and inactivation of their common receptor Patched, a twelve-transmembrane protein that otherwise would suppress activity of the seven-transmembrane protein, Smoothened. Loss of Patched function, the most common cause of basal cell carcinoma, permits unregulated activation of Smoothened and of the Hedgehog pathway. A cryo-EM structure of the Patched protein reveals striking transmembrane domain similarities to prokaryotic RND transporters. The extracellular domain mediates association of Patched monomers in an unusual dimeric architecture that implies curvature in the associated membrane. A central conduit with cholesterol-like contents courses through the extracellular domain and resembles that used by other RND proteins to transport substrates, suggesting Patched activity in cholesterol transport. Patched expression indeed reduces cholesterol activity in the inner leaflet of the plasma membrane, in a manner antagonized by Hedgehog stimulation and with implications for regulation of Smoothened.

scholarly journals Structural basis for activation of plasma-membrane Ca2+-ATPase by calmodulin

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Julius Nitsche ◽  
Inokentijs Josts ◽  
Johannes Heidemann ◽  
Haydyn D. Mertens ◽  
Selma Maric ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Structural Basis

Lipoprotein in cholesterol transport: Highlights and recent insights into its structural basis and functional mechanism

2018 ◽  
Vol 27 (2) ◽  
pp. 028702
Author(s):  
Shu-Yu Chen ◽  
Na Li ◽  
Tao-Li Jin ◽  
Lu Gou ◽  
Dong-Xiao Hao ◽  
...  
Keyword(s):  
Structural Basis ◽  
Cholesterol Transport ◽  
Functional Mechanism

Fine-Structural Localization of Adenosine Triphosphatase in the Rectum of Calliphora

1968 ◽  
Vol 3 (1) ◽  
pp. 17-32
Author(s):  
M. J. BERRIDGE ◽  
B. L. GUPTA
Keyword(s):  
Plasma Membrane ◽  
Adenosine Triphosphatase ◽  
Plasma Membranes ◽  
Fluid Transport ◽  
Microsomal Fraction ◽  
Adenosine Diphosphate ◽  
Structural Basis ◽  
Osmotic Gradient ◽  
Ph Optimum ◽  
Structural Localization

Adenosine triphosphatase (ATPase) activity in the rectal papillae of Calliphora has been studied by biochemical and histochemical techniques. The microsomal fraction contained a Mg2+-activated ATPase with a pH optimum of 8.0. The enzyme was not stimulated by the addition of Na+ plus K+ and was insensitive to ouabain. Histochemical studies using modifications of the Wachstein-Meisel method showed that at pH 7.2 this Mg2+-activated ATPase was specifically localized on the intracellular surface of the lateral plasma membranes. A similar though less intense reaction was obtained with adenosine diphosphate and inosine triphosphate, but not with guanosine triphosphate, uridine triphosphate or β-glycerophosphate as substrates. At an acid pH (6.6-6.8), very little reaction occurred on the lateral plasma membrane but some reaction product was present in mitochondria and nuclei. Very little enzyme activity was found in the flattened rectal epithelium. These results are discussed in relation to the available data on transport ATPases and on the structural basis of fluid transport by rectal papillae. It is proposed that the ATPase localized on the stacks of lateral plasma membrane may be involved with ion secretion into the intercellular spaces to create the osmotic gradient necessary to extract water from the lumen.

Fine-Structural Aspects of Fertilization in Chlamydomonas Reinhardi

1968 ◽  
Vol 3 (1) ◽  
pp. 115-128
Author(s):  
I. FRIEDMANN ◽  
A. L. COLWIN ◽  
LAURA H. COLWIN
Keyword(s):  
Plasma Membrane ◽  
Mating Type ◽  
Starch Content ◽  
The Body ◽  
Structural Basis ◽  
Basal Bodies ◽  
Cytoplasmic Organelle ◽  
Animal Phyla ◽  
Small Structure ◽  
Specialized Structure

Gametes of C. reinhardi lack the cell wall which vegetative cells possess. Just below the cell apex gametes form a fertilization tubule which is up to 2 µ long and 0.2 µ in diameter; its plasma membrane and that of the apex have slender tubular projections. At the base of the fertilization tubule regularly lies the choanoid body, a collar-shaped cytoplasmic organelle; the plasma membrane overlying the body appears as an electron-dense ring. Gametes possess two ‘free’ basal bodies in addition to the basal bodies of the two flagella. In the initial stage of union the conjugating cells are connected by the fertilization tubule whose plasma membrane is continuous with that of both copulants. At one end of the tubule lies a conspicuous choanoid body, but at the other end is a small structure which possibly is a homologue of the choanoid body. Subsequently, the fertilization tubule shortens and widens until finally no tubule exists and the apical ends of the two protoplasts adjoin. The merging cells then bend like a jack-knife and lateral alignment of the protoplasts occurs. This four-flagellated zygote becomes motile at about the time when the flagellar bases of the former gametes seem to approach each other and when fibrillar elements of the flagellar roots come into contact. In the motile zygote the nuclei do not fuse but remain ensheathed in the cup-shaped plastids of the two gametes. A mating of plus (+) and minus (-) strains cultured, respectively, for high and low starch content suggested that gametes of only the plus (+) mating type contain the choanoid body. Since it appears that the gamete containing the choanoid body also produces the fertilization tubule, it is inferred that gametes of only the plus (+) mating type produce the fertilization tubule. Should further investigation support this inference, it would be established that there is a structural basis for designating the plus (+) mating type as male and the minus (-) type as female. Fertilization involves fusion of the gamete membranes through the mediation of a specialized structure (the fertilization tubule) and in this respect there are similarities to certain aspects of fertilization in animal phyla. The relation of the fertilization tubule to the protoplasmic bridge of other species of Chlamydomonas is discussed.

scholarly journals Structural Basis and Functional Mechanism of Lipoprotein in Cholesterol Transport

2018 ◽  
Author(s):  
Zhiwei Yang ◽  
Dongxiao Hao ◽  
Yizhuo Che ◽  
Lei Zhang ◽  
Shengli Zhang
Keyword(s):  
Structural Basis ◽  
Cholesterol Transport ◽  
Functional Mechanism

scholarly journals Structural basis for targeting HIV-1 Gag proteins to the plasma membrane for virus assembly

2006 ◽  
Vol 103 (30) ◽  
pp. 11364-11369 ◽  
Author(s):  
J. S. Saad ◽  
J. Miller ◽  
J. Tai ◽  
A. Kim ◽  
R. H. Ghanam ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Virus Assembly ◽  
Structural Basis ◽  
Gag Proteins ◽  
Hiv 1

scholarly journals Structural basis for plant plasma membrane protein dynamics and organization into functional nanodomains

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Julien Gronnier ◽  
Jean-Marc Crowet ◽  
Birgit Habenstein ◽  
Mehmet Nail Nasir ◽  
Vincent Bayle ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Secretory Pathway ◽  
Super Resolution ◽  
Lipid Binding ◽  
Single Particle Tracking ◽  
Structural Basis ◽  
Binding Motif ◽  
Supramolecular Organization ◽  
Hormonal Crosstalk ◽  
Definition Of

Plasma Membrane is the primary structure for adjusting to ever changing conditions. PM sub-compartmentalization in domains is thought to orchestrate signaling. Yet, mechanisms governing membrane organization are mostly uncharacterized. The plant-specific REMORINs are proteins regulating hormonal crosstalk and host invasion. REMs are the best-characterized nanodomain markers via an uncharacterized moiety called REMORIN C-terminal Anchor. By coupling biophysical methods, super-resolution microscopy and physiology, we decipher an original mechanism regulating the dynamic and organization of nanodomains. We showed that targeting of REMORIN is independent of the COP-II-dependent secretory pathway and mediated by PI4P and sterol. REM-CA is an unconventional lipid-binding motif that confers nanodomain organization. Analyses of REM-CA mutants by single particle tracking demonstrate that mobility and supramolecular organization are critical for immunity. This study provides a unique mechanistic insight into how the tight control of spatial segregation is critical in the definition of PM domain necessary to support biological function.

scholarly journals Model for the architecture of caveolae based on a flexible, net-like assembly of Cavin1 and Caveolin discs

2016 ◽  
Vol 113 (50) ◽  
pp. E8069-E8078 ◽  
Author(s):  
Miriam Stoeber ◽  
Pascale Schellenberger ◽  
C. Alistair Siebert ◽  
Cedric Leyrat ◽  
Ari Helenius ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Complex Formation ◽  
Membrane Binding ◽  
Coiled Coil ◽  
Structural Basis ◽  
Membrane Domains ◽  
Coiled Coil Domain ◽  
Regular Dodecahedron ◽  
Plasma Membrane Domains ◽  
Electron Cryotomography

Caveolae are invaginated plasma membrane domains involved in mechanosensing, signaling, endocytosis, and membrane homeostasis. Oligomers of membrane-embedded caveolins and peripherally attached cavins form the caveolar coat whose structure has remained elusive. Here, purified Cavin1 60S complexes were analyzed structurally in solution and after liposome reconstitution by electron cryotomography. Cavin1 adopted a flexible, net-like protein mesh able to form polyhedral lattices on phosphatidylserine-containing vesicles. Mutating the two coiled-coil domains in Cavin1 revealed that they mediate distinct assembly steps during 60S complex formation. The organization of the cavin coat corresponded to a polyhedral nano-net held together by coiled-coil segments. Positive residues around the C-terminal coiled-coil domain were required for membrane binding. Purified caveolin 8S oligomers assumed disc-shaped arrangements of sizes that are consistent with the discs occupying the faces in the caveolar polyhedra. Polygonal caveolar membrane profiles were revealed in tomograms of native caveolae inside cells. We propose a model with a regular dodecahedron as structural basis for the caveolae architecture.

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