Caveolin-1 isoform reorganization studied by image correlation spectroscopy.
Caveolae are small, flask shaped invaginations in the cell membrane. They are thought to play a crucial role in cell signaling, endocytosis and intracellular cholesterol transport. Caveolin-1, 2 and 3 are key proteins, which are important for the formation of the invaginations on the cell surface. Caveolin-1 exists in two isoforms: caveolin-1 alpha (a) and caveolin-1 beta (beta). Little is known about the difference between these two isoforms, and less in known about their role in cell signaling. Bone morphogenetic proteins IBMPs) are a subfamily of the TGF beta superfamily and their response is mediated by serine/threonine kinase receptors. Epidermal growth factor (EGF) is known to signal through tyrosine kinase receptors of the ErbB family. Here we report on the aggregation and association of caveolin-1 isoforms with these receptors and the effect of BMP and EGF activation on caveolin-1 distribution in A431 cells. Our data, obtained by application of a family of image correlation spectroscopy tools, indicate that BMP and EGF stimulation lead to a rearrangement of the caveolin-1 isoforms on the cell surface. BMP as well as EGF stimulation leads to a rearrangement of the caveolin-1 P isoform into domains enriched in the caveolin-1 alpha isoform. We further show that about 20-30% of the caveolin-1 present at the surface of the cells co-localize with the EGF and BMP receptors. Using a reporter gene assay sensitive to the activation of the BMP pathway, we show that overexpression of caveolin-1beta inhibits signaling. Our data suggest that the two isoforms of caveolin-1 play different roles on the cell surface and that caveolae are dynamic structures.
Department of Chemistry, University of Western Ontario, London, Canada.
Anja
A
Nohe
Eleonora
E
Keating
Crystal
C
Loh
Michael T
MT
Underhill
Nils O
NO
Petersen
D000465:Algorithms; D019485:Bone Morphogenetic Proteins / Q000096:biosynthesis / Q000737:chemistry; D051242:Caveolin 1; D022461:Caveolins / Q000737:chemistry*; D066246:ErbB Receptors / Q000096:biosynthesis / Q000737:chemistry; D005455:Fluorescent Antibody Technique; D017930:Genes, Reporter; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007536:Isomerism; D008156:Luciferases / Q000235:genetics; D018613:Microscopy, Confocal; D013057:Spectrum Analysis
D019485:Bone Morphogenetic Proteins; C495540:CAV1 protein, human; D051242:Caveolin 1; D022461:Caveolins; D008156:Luciferases; D066246:ErbB Receptors