Non Receptor Tyrosine Kinases and Insulin Induced Caveolin Phosphorylation

Significant data had linked activation of Src-family kinases to caveolin phosphor-ylation. Therefore, it was initially hypothesized that a Src-family kinase was the insulin-stimulated caveolin-tyrosine kinase in adipocytes. Consistent with this, treatment of isolated caveolar fractions with Src-family kinase inhibitors blocked caveolin phosphorylation in vitro, indicating that the caveolin kinase activity that co-purifies with caveolin is a Src-family kinase (CCM, unpublished observation 16 )....

Angiogenesis and CaveolineNOS Interaction

In 1999, Lisanti and colleagues documented that caveolin-1 was down-regulated by angiogenic growth factors in subconfluent endothelial cells, but not when these cells were confluent 42 . These authors further showed that, in contrast, caveolin-1 protein levels were up-regulated during endothelial cell differentiation and that expression of caveolin-1 in confluent endothelial cells stimulated endothelial tube formation 43 . Although, the original observation that growth factor exposure can...

Vasodilation Endothelial Permeability and CaveolineNOS Interaction

The role of caveolae in endothelium-dependent and NO-mediated vascular relaxation was documented in the original papers reporting the phenotype of caveolin-deficient mice by the groups of Kurzchalia and Lisanti 48,49 . These authors have, indeed, evaluated the NO-mediated vasorelaxing effects of acetylcholine on aortic rings precontracted with phenylephrine (an a1-adrenergic vasoconstrictor). Both groups reported a significantly greater relaxation in Cav-1 null aortic rings at all acetylcholine...

The Caveolins are not Direct Substrates of the Insulin Receptor

Insulin binding to its receptor at the cell surface causes a conformational change in the intracellular domain of the receptor, leading to auto-transphosphorylation of the receptor. This autophosphorylation in turn activates the kinase domain, leading to the phosphorylation of direct substrates, including insulin receptor sub-strate-1 (IRS-1). Since the insulin receptor is associated with caveolae 14,57,58 , it was possible that caveolin was a direct substrate of the insulin receptor itself....

Divergent Expression of Caveolin1 in Human Cancer The Case of Lung Cancer

The expression of caveolin-1 in different cancer cell lines and tumor samples was documented in numerous studies, and the picture that emerges from these studies is that caveolin-1 expression is highly divergent 6 . Whereas in many cases caveolin-1 expression is down-regulated, in other cancer cells elevated caveolin-1 levels are maintained. High expression of caveolin-1 in cancer cells was initially demonstrated in human multidrug resistant (MDR) cancer cells 43-45 and in mouse metastatic...

FC Binding by Proteins Including Caveolin

In contrast to reviews of protein-protein and protein-DNA binding, very few studies have been made of the structural aspects of FC binding to proteins. The sum of evidence available suggests that FC lies within a hydrophobic cleft or tunnel, the sides of which are composed of several different hydrophobic sequences organized by the tertiary structure of the native protein. A positively charged amino acid K or R may contribute to a charge clamp stabilizing the 3P-OH group. Whilst the volume of...

Insulin Induced Actin Remodeling GluT4 Translocation and Caveolae

Adipocytes are terminally differentiated and are not dividing. They are also not migrating or spreading on the extracellular matrix, and they do not have well-formed stress fibers. Therefore, what is the significance of caveolin phosphorylation and Csk-induced attenuation of Src-family kinase activity in response to insulin in these cells Insulin increases glucose transport in fat and muscle cells by stimulating the translocation of GluT4 from intracellular vesicles to the plasma membrane....

The Dynamics of Caveolin and Actin

Ultrastructural and biochemical analyses have implicated the actin cytoskeleton as having a role in caveolae function 21-24 . Caveolin is also involved in dynamic actin remodeling in endocytosis or molecular trafficking. In adipocytes, the stimulation of glucose uptake by insulin is achieved via the translocation of intracellular glucose transporter 4 GLUT4 to the cell-surface membrane. Insulin-induced GLUT4 translocation in adipocytes requires dynamic actin remodeling at the inner surface of...

Feedback Inhibition of Fyn Through Activation of

These data support the following model Fig. 6.4 . Activation of Fyn in caveolae by insulin or stress leads to phosphorylation of caveolin-1 on Tyr14, which leads to the recruitment of Csk, and phosphorylation and inhibition of resident Src-family kinases. This feedback mechanism is supported by a number of observations 24,31 . Oxidative stress simultaneously activates Src-family kinases and their negative regulator Csk. Induction of oxidative stress leads to concomitant increases in both active...

Organization and Function of Receptor Tyrosine Kinases is Linked to Lipid Microdomains

Lipid Raft Detection Snom

Receptor tyrosine kinases are prominent examples of the proteins involved in cell signaling that form molecular associations and superstructures in the cell membrane. Cooperative interactions between or among receptor tyrosine kinases play a pivotal role in signal transduction. This includes homo- and hetero-dimerizations as well as potentially higher-order associations, which may be either dependent or independent of ligands. In addition to protein-protein interactions, lipid microdomains also...

Caveolin Diffusion Coefficients

AA see amino acid Ab see amyloid b-peptide ABCA1 see ATP-binding cassette - caveolin phosphorylation 121 acceptor, fluorescence correlation spectroscopy 59 acceptor channels, FRET 146 ACTH see adrenocorticotropic actin plasma membrane attachment sites, phosphorylation 128 actin polymerization 131 actin remodeling 127 - insulin-induced 131 activation, Csk 125-127 activation-induced cell death AICD , lipid rafts 157 acylation, signal transduction 92 AD see Alzheimer's disease ADAM10,...

The Immunological Synapse

Lipid Raft Detection Snom

One of the best-characterized examples of specialized signaling domains where the dynamic assembly of both small- and large-scale protein associations have a crucial role, is the contact region formed between a T cell and a target or an antigen-presenting cell APC , termed the immunological synapse IS 63,64 . Formation of the IS is initiated by recognition of the peptide antigen presented in complex with MHC glycoproteins on the APC or target cell by the T cell receptor complex TCR on the...

Molecular Mechanisms Implicated in the Pro Survival Action of Caveolin1

Cell Prosurvivial Image

The phosphoinositide 3-kinase PI3K Akt cell survival pathway has recently emerged as a major target for regulation by caveolin-1 in a variety of cancer cells 12,13,86 . A possible role of caveolin-1 in PI3K Akt pathway activation was shown in multiple myeloma cells which, unlike most other hematopoietic-derived cells, express high levels of caveolin-1 86 . Caveolin-1 was found to co-localize in lipid rafts fractions, and to co-exist in an immunoprecipitable complex, with receptors for...

Introduction

Py14 Caveolin

Caveolae are specialized invaginated domains of the plasma membrane that act as organizing centers for signaling molecules. Caveolae are formed in membranes by the caveolins, a family of three related gene products caveolins-1, -2, and -3 1-4 . Caveolins form homo- and hetero-oligomers that make up the characteristic striated coat of caveolae 5 . Expression of caveolin is necessary and sufficient to induce cell-surface caveolae 6-8 . In addition to their role as coat proteins that drive the...

The Origin of the Raft Hypothesis

Fluid Mosaik Modell

Membrane heterogeneities resurfaced primarily as a necessity to explain a specific biological observation of preferential sorting of glycosphingolipids to apical membranes in polarized epithelial cells 4 . This idea was finally developed into a notion of lipid rafts by Simons and coworkers, and was centered on cholesterol-containing domains as the cornerstone of the raft model of life in a living cell membrane 5 Fig. 3.2A . Lipid rafts were hypothesized as specialized regions of cell membrane...

Proximity Measurement Using HomoFRET

Gpi Anchor Plant

Homo-FRET measures the loss of fluorescence anisotropy, resulting from the FRET process. It is a relatively less well-known approach to FRET, and is also referred to as depolarization-FRET 74,75 . In this type of FRET, fluorescence emission excited by polarized light is measured for the extent of loss of fluorescence anisotropy using appropriately placed excitation and emission polarizers Fig. 3.6 . Due to a finite spread of allowed angular dependence between the donor and acceptor...

References

Detergent-insoluble glycos-phingolipid cholesterol-rich membrane do mains, lipid rafts and caveolae review . Mol. Membr. Biol. 16 145-156, 1999. 2 Iwabuchi K, Handa K, Hakomori S. Separation of glycosphingolipid-enriched microdomains from caveolar membrane characterized by presence of caveolin. Methods Enzymol. 312 488-494, 2000. 3 Smart EJ, Graf GA, McNiven MA, Sessa WC, Engelman JA, Scherer PE, Okamoto T, Lisanti MP. Caveolins, liquid-ordered domains, and signal transduction....