Membrane cholesterol and the regulation of signal transduction

2004 ◽  
Vol 32 (1) ◽  
pp. 65-69 ◽  
Author(s):  
C.J. Fielding ◽  
P.E. Fielding
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Lipid Rafts ◽  
Mammalian Cells ◽  
Protein Composition ◽  
Cholesterol Content ◽  
Membrane Cholesterol ◽  
Transmembrane Signalling

The plasma membrane of mammalian cells consists of microdomains differing in lipid and protein composition. Two distinct classes of cholesterol/sphingolipid microdomain (caveolae and lipid rafts) are assembly points for transmembrane signalling complexes. Recent evidence suggests that transient changes in cholesterol content may be important in regulating signal transduction.

scholarly journals Modulation of ileal bile acid transporter (ASBT) activity by depletion of plasma membrane cholesterol: association with lipid rafts

2008 ◽  
Vol 294 (2) ◽  
pp. G489-G497 ◽  
Author(s):  
Fadi Annaba ◽  
Zaheer Sarwar ◽  
Pradeep Kumar ◽  
Seema Saksena ◽  
Jerrold R. Turner ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Bile Acid ◽  
Lipid Rafts ◽  
Cholesterol Content ◽  
Membrane Cholesterol ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Bile Acid Transporter ◽  
Acid Transporter

Apical sodium-dependent bile acid transporter (ASBT) represents a highly efficient conservation mechanism of bile acids via mediation of their active transport across the luminal membrane of terminal ileum. To gain insight into the cellular regulation of ASBT, we investigated the association of ASBT with cholesterol and sphingolipid-enriched specialized plasma membrane microdomains known as lipid rafts and examined the role of membrane cholesterol in maintaining ASBT function. Human embryonic kidney (HEK)-293 cells stably transfected with human ASBT, human ileal brush-border membrane vesicles, and human intestinal epithelial Caco-2 cells were utilized for these studies. Floatation experiments on Optiprep density gradients demonstrated the association of ASBT protein with lipid rafts. Disruption of lipid rafts by depletion of membrane cholesterol with methyl-β-cyclodextrin (MβCD) significantly reduced the association of ASBT with lipid rafts, which was paralleled by a decrease in ASBT activity in Caco-2 and HEK-293 cells treated with MβCD. The inhibition in ASBT activity by MβCD was blocked in the cells treated with MβCD-cholesterol complexes. Kinetic analysis revealed that MβCD treatment decreased the Vmax of the transporter, which was not associated with alteration in the plasma membrane expression of ASBT. Our study illustrates that cholesterol content of lipid rafts is essential for the optimal activity of ASBT and support the association of ASBT with lipid rafts. These findings suggest a novel mechanism by which ASBT activity may be rapidly modulated by alterations in cholesterol content of plasma membrane and thus have important implications in processes related to maintenance of bile acid and cholesterol homeostasis.

Regulation of ecto-5′-nucleotidase activity via Ca2+-dependent, annexin 2-mediated membrane rearrangement?

2006 ◽  
Vol 34 (3) ◽  
pp. 374-376 ◽  
Author(s):  
E.B. Babiychuk ◽  
A. Draeger
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Lipid Rafts ◽  
Binding Proteins ◽  
Extracellular Atp ◽  
Membrane Rafts ◽  
Nucleotidase Activity ◽  
Annexin 2 ◽  
Associated Proteins ◽  
A Cell

The spatial segregation of the plasma membrane plays a prominent role in distinguishing and sorting a large number of signals a cell receives simultaneously. The plasma membrane comprises regions known as lipid rafts, which serve as signal-transduction hubs and platforms for sorting membrane-associated proteins. Ca2+-binding proteins of the annexin family have been ascribed a role in the regulation of raft dynamics. Glycosylphosphatidylinositol-anchored 5′-nucleotidase is an extracellular, raft-associated enzyme responsible for conversion of extracellular ATP into adenosine. Our results point to a regulation of ecto-5′-nucleotidase activity by Ca2+-dependent, annexin-mediated stabilization of membrane rafts.

Direct Electrochemical Evaluation of Plasma Membrane Cholesterol in Live Mammalian Cells

2007 ◽  
Vol 129 (37) ◽  
pp. 11352-11353 ◽  
Author(s):  
Dechen Jiang ◽  
Anando Devadoss ◽  
M. Simona Palencsár ◽  
Danjun Fang ◽  
Nicole M. White ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Mammalian Cells ◽  
Membrane Cholesterol ◽  
Electrochemical Evaluation ◽  
Plasma Membrane Cholesterol

scholarly journals Pretreatment of Asian elephant (Elephas maximus) spermatozoa with cholesterol-loaded cyclodextrins and glycerol addition at 4°C improves cryosurvival

2012 ◽  
Vol 24 (8) ◽  
pp. 1134 ◽  
Author(s):  
Wendy K. Kiso ◽  
Atsushi Asano ◽  
Alexander J. Travis ◽  
Dennis L. Schmitt ◽  
Janine L. Brown ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Culture Medium ◽  
Egg Yolk ◽  
Cholesterol Content ◽  
Asian Elephant ◽  
Elephas Maximus ◽  
Membrane Cholesterol ◽  
Captive Management ◽  
Sperm Survival ◽  
Cryopreservation Method

Asian elephant spermatozoa are sensitive to chilling and do not respond well to cryopreservation. The objectives of the present study were to: (1) determine whether cholesterol content can be modified by preincubation of Asian elephant spermatozoa with cholesterol-loaded cyclodextrin (CLC); and (2) assess the effects of CLC concentration(s), temperature at time of glycerol addition (22°C vs 4°C) and dilution medium on post-thaw sperm survival. Spermatozoa incubated with ≥1.5 mg CLC exhibited increased (P < 0.05) cholesterol concentrations. Pretreatment of spermatozoa with 1.5 mg CLC resulted in improvements (P < 0.05) in all post-thaw parameters. Glycerol addition at 4°C also improved all post-thaw parameters compared with 22°C. Dilution of thawed spermatozoa in an egg yolk-based medium improved (P < 0.05) motility compared with Ham’s F-10 culture medium. In summary, our findings indicate that modifying cholesterol content within the plasma membrane improves the cryosurvival of Asian elephant spermatozoa. The development of an improved cryopreservation method that includes modification of membrane cholesterol and the addition of glycerol at 4°C, as reported in the present study, is an important step towards utilisation of cryopreserved spermatozoa in captive management of this species.

scholarly journals Reprogramming cholesterol metabolism in macrophages and its role in host defense against cholesterol-dependent cytolysins

2022 ◽  
Author(s):  
Min-Sub Lee ◽  
Steven J. Bensinger
Keyword(s):  
Plasma Membrane ◽  
Host Defense ◽  
Mammalian Cells ◽  
Cholesterol Metabolism ◽  
Current Knowledge ◽  
Membrane Integrity ◽  
Cholesterol Homeostasis ◽  
Metabolic Reprogramming ◽  
Membrane Cholesterol ◽  
Plasma Membrane Cholesterol

AbstractCholesterol is a critical lipid for all mammalian cells, ensuring proper membrane integrity, fluidity, and biochemical function. Accumulating evidence indicates that macrophages rapidly and profoundly reprogram their cholesterol metabolism in response to activation signals to support host defense processes. However, our understanding of the molecular details underlying how and why cholesterol homeostasis is specifically reshaped during immune responses remains less well understood. This review discusses our current knowledge of cellular cholesterol homeostatic machinery and introduces emerging concepts regarding how plasma membrane cholesterol is partitioned into distinct pools. We then discuss how proinflammatory signals can markedly reshape the cholesterol metabolism of macrophages, with a focus on the differences between MyD88-dependent pattern recognition receptors and the interferon signaling pathway. We also discuss recent work investigating the capacity of these proinflammatory signals to selectively reshape plasma membrane cholesterol homeostasis. We examine how these changes in plasma membrane cholesterol metabolism influence sensitivity to a set of microbial pore-forming toxins known as cholesterol-dependent cytolysins that specifically target cholesterol for their effector functions. We also discuss whether lipid metabolic reprogramming can be leveraged for therapy to mitigate tissue damage mediated by cholesterol-dependent cytolysins in necrotizing fasciitis and other related infections. We expect that advancing our understanding of the crosstalk between metabolism and innate immunity will help explain how inflammation underlies metabolic diseases and highlight pathways that could be targeted to normalize metabolic homeostasis in disease states.

Requirement of Lipid Raft Integrity for Signaling by JAK2-V617F

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4191-4191
Author(s):  
Lori N. Griner ◽  
Kathy L. McGraw ◽  
Joseph O. Johnson ◽  
Alan F. List ◽  
Gary W. Reuther
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Complex Formation ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Kinase Activity ◽  
Jak2 V617f ◽  
Cytokine Receptors ◽  
Downstream Signaling ◽  
Stat Signaling

Abstract Abstract 4191 JAK2 is a cytoplasmic tyrosine kinase that plays an important role in signaling following activation of various cytokine receptors. JAK2 activation promotes growth, survival, and differentiation of various cell types. Mutation of JAK2 is seen in numerous hematopoietic diseases, most notably in myeloproliferative neoplasms (MPNs). JAK2-V617F is a frequent mutation found in the classical MPNs: polycythemia vera, essential thrombocythemia, and primary myelofibrosis. The single amino acid change of valine to phenylalanine occurs in the pseudokinase domain of JAK2, relieving auto-inhibition of the kinase domain and allowing constitutive kinase activity. Numerous mouse models have demonstrated that JAK2-V617F can induce MPN-like disorders in mice. Thus, this point mutation, as well as other less common JAK2 mutations, is believed to play an important etiologic role in the development of MPNs in humans. The development and use of JAK2 inhibitors in clinical trials has shown promising results, again demonstrating the important role JAK2 plays in MPNs. While the JAK2-V617F mutation, as well as other JAK2 mutations, decreases auto-inhibition of JAK2 kinase activity, it is clear that mutated JAK2 still requires the expression of cytokine receptors to induce activation of transforming signals in hematopoietic cells. Normally, JAK2 binds to homodimeric and heterodimeric cytokine receptors through specific receptor motifs and is activated by various structural changes induced by cytokine stimulation. Following activation it utilizes receptor tyrosines as substrates for phosphorylation, leading to recruitment of downstream signaling molecules, such as STAT5, among others. JAK2 then activates STAT5 via phosphorylation and STAT5 then translocates to the nucleus to regulate transcription of target genes. JAK2-V617F does not require ligand for activation, but still requires the scaffolding function of cytokine receptors to facilitate its full activation and activation of downstream signaling via phosphorylation. Lipid rafts are microdomains of the plasma membrane that are enriched in cholesterol and sphingolipids. They have gained appreciation in signal transduction as sites of localization of signaling mediators, including membrane-bound receptors. Congregation of signaling proteins in lipid rafts within the plasma membrane promotes complex formation and signaling cascade activation. We have recently demonstrated that JAK2 is present in lipid rafts during erythropoietin signaling and that lipid raft integrity is required for erythropoietin-mediated signal transduction (Blood 2009, 114: 292). In our current study, we demonstrate that constitutive JAK-STAT signaling driven by JAK2-V617F is sensitive to lipid raft disruption. Human erythroleukemia (HEL) cells express constitutive activation of JAK-STAT signaling due to the presence of JAK2-V617F. Treatment of these cells with methyl-beta-cyclodextrin to disrupt lipid rafts abolished JAK2, STAT5, and STAT3 activation. Similar results are obtained in other cell lines harboring JAK2-V617F and that exhibit JAK-STAT activation that is dependent on this activated form of JAK2. We also demonstrate that JAK2-V617F co-localizes with lipid rafts, as shown by immunofluorescence, and that this co-localization is abolished by lipid raft disruption. This suggests the loss of JAK2-V617F-mediated JAK-STAT activation we observe following lipid raft disruption may be due to an inhibition of properly localized protein complex formation in the plasma membrane that is necessary for JAK2-V617F signaling. Lipid rafts may provide a site for an accumulation of JAK2-V617F-containing signaling complexes and may be necessary for the cellular signals initiated by JAK2-V617F. Our data show JAK2-V617F-driven JAK-STAT pathway activation is vulnerable to lipid raft disrupting agents and suggest lipid raft integrity as a potential therapeutic target for JAK2-V617F positive neoplasms. Targeting lipid rafts in combination with JAK2 kinase inhibitors may allow for more effective kinase inhibition at lower doses, potentially decreasing undesirable side effects associated with kinase inhibitor treatment. Disclosures: No relevant conflicts of interest to declare.

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