title: Flotillins/cavatellins are differentially expressed in cells and tissues and form a hetero-oligomeric complex with caveolins in vivo. Characterization and epitope-mapping of a novel flotillin-1 monoclonal antibody probe.
abstract: Caveolae are vesicular organelles that represent a subcompartment of the plasma membrane. Caveolins and flotillins are two families of mammalian caveolae-associated integral membrane proteins. However, it remains unknown whether flotillins interact with caveolin proteins to form a stable caveolar complex or if expression of flotillins can drive vesicle formation. Here, we examine the cell type and tissue-specific expression of the flotillin gene family. For this purpose, we generated a novel monoclonal antibody probe that recognizes only flotillin-1. A survey of cell and tissue types demonstrates that flotillins 1 and 2 have a complementary tissue distribution. At the cellular level, flotillin-2 was ubiquitously expressed, whereas flotillin-1 was most abundant in A498 kidney cells, muscle cell lines, and fibroblasts. Using three different models of cellular differentiation, we next examined the expression of flotillins 1 and 2. Taken together, our data suggest that the expression levels of flotillins 1 and 2 are independently regulated and does not strictly correlate with known expression patterns of caveolin family members. However, when caveolins and flotillins are co-expressed within the same cell, as in A498 cells, they form a stable hetero-oligomeric "caveolar complex." In support of these observations, we show that heterologous expression of murine flotillin-1 in Sf21 insect cells using baculovirus-based vectors is sufficient to drive the formation of caveolae-like vesicles. These results suggest that flotillins may participate functionally in the formation of caveolae or caveolae-like vesicles in vivo. Thus, flotillin-1 represents a new integral membrane protein marker for the slightly larger caveolae-related domains (50-200 nm) that are observed in cell types that fail to express caveolin-1. As a consequence of these findings, we propose the term "cavatellins" be used (instead of flotillins) to describe this gene family.
authors.affiliation: Department of Molecular Pharmacology and The Albert Einstein Cancer Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: D
authors.initials: D
authors.lastname: Volonte
authors.forename: F
authors.initials: F
authors.lastname: Galbiati
authors.forename: S
authors.initials: S
authors.lastname: Li
authors.forename: K
authors.initials: K
authors.lastname: Nishiyama
authors.forename: T
authors.initials: T
authors.lastname: Okamoto
authors.forename: M P
authors.initials: MP
authors.lastname: Lisanti
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology*; D001704:Biopolymers; D051242:Caveolin 1; D022461:Caveolins; D002454:Cell Differentiation; D002460:Cell Line; D018604:Epitope Mapping; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015335:Molecular Probes; D008969:Molecular Sequence Data; D011485:Protein Binding; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D001704:Biopolymers; C495540:CAV1 protein, human; D051242:Caveolin 1; D022461:Caveolins; D008565:Membrane Proteins; D015335:Molecular Probes; D011994:Recombinant Proteins; C106354:flotillins