Caveolae
Caveolae are 50 to 100 nanometer large, sack-shaped indentations in the plasma membrane that can be seen under the electron microscope on the surface of different cell types.
Caveolae are special lipid rafts with a typical composition of proteins and lipids. The protein caveolin is the most important structural element.
meaning
Caveolae play an important role in mechanotransduction , and dysfunction can be associated with a number of medical conditions.
Caveolae occur in most cells, but are particularly numerous in some, e.g. B. in the vascular endothelium, on fat cells and smooth muscle cells. Caveolae constrict in the vascular endothelium and presumably serve for the transcytosis of plasma proteins (transendothelial exchange of substances). In muscle, fat and other cells, on the other hand, caveolae remain on the surface as stationary pits and are probably preferred microdomains for the coupling between membrane receptors and intracellular signal cascades, because the caveolae membrane is particularly rich in receptors for various physiological agents (e.g. Insulin).
Since the discovery of the caveolae, their role in endocytosis has been discussed - probably because of their morphological similarity to the so-called " clathrin coated pits". However, findings indicate that these are static structures that internalize very slowly, but can be induced to do so in the model.
It is now considered proven that they also play a crucial role in the development of Alzheimer's disease and a form of muscular dystrophy , but this is true for lipid rafts in general or for caveolin -3 in muscles. ESA / reggie is also important as a component in endothelia with caveolin-1 and -2. This protein is involved in mechanotransduction (this has been proven at least in the model organism of the nematode C. elegans using a homologue).
Caveolae and Oncogenesis
It was found that both too much and too little of caveolin in a cell correlate with their degeneration. Signal transduction acts as an important link.
Caveolae and idiopathic pulmonary fibrosis
In patients with idiopathic pulmonary fibrosis , the expression of caveolin-1 in the lung tissue is markedly reduced. Transforming growth factor ß1 (TGF-ß1) , a cytokine that promotes the multiplication of connective tissue , inhibits the expression of caveolin-1 in fibroblasts of the human lung . Conversely, caveolin-1 in cultivated fibroblasts inhibits the TGF-ß1-induced production of extracellular matrix .
Caveolae and kidney damage in high blood pressure
In the kidney corpuscles , increased blood pressure leads to the upregulation of Ras homolog gene family, member A (RhoA) of a small GTP-ase from the RAS superfamily . Caveolae and caveolin-1 play an important role in transmitting mechanical stress signals. The upregulation of RhoA leads to increased production of extracellular matrix and this in turn is an important mechanism for high pressure-induced kidney damage (nephrosclerosis) .
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- ↑ Xiao Mei Wang et al .: Caveolin-1: a critical regulator of lung fibrosis in idiopathic pulmonary fibrosis. In: Journal of Experimental Medicine . No. 203 , 2006, pp. 2895-2906 ( Article Abstract ).
- ↑ Fangfang Peng et al .: RhoA Activation in Mesangial Cells by Mechanical Strain Depends on Caveolae and Caveolin-1 Interaction . In: J Am Soc Nephrol . No. 18 , 2007, p. 189-198 ( article abstract ).