Identification, sequence and developmental expression of invertebrate flotillins from Drosophila melanogaster

Caveolae are vesicular organelles that represent a sub-compartment of the plasma membrane. Caveolins (Cav-1, -2 and -3) and flotillins (FLO-1 and FLO-2 [also known as epidermal surface antigens (ESAs)] are two families of mammalian caveolae-associated integral membrane proteins. Although a caveolin gene family has recently been described in the invertebrate Caenorhabditis elegans, it remains unknown as to whether flotillin homologues exist in invertebrates. Here, we report the identification, cDNA sequence and embryonic expression pattern of the first invertebrate flotillin, i.e. flotillin from Drosophila melanogaster (FLODm). FLODm is most closely related to mammalian flotillin-1. Remarkably, the invertebrate FLODm protein behaves like mammalian flotillins and is targeted to the caveolae-enriched membrane fraction after transient expression in mammalian cells. Localization of the FLODm message in D. melanogaster embryos reveals that expression of FLODm is confined primarily to the developing nervous system. This is consistent with our previous observation that mammalian flotillin-1 mRNA and protein is expressed abundantly in brain tissue. Interestingly, the FLODm gene is localized to chromosomal region 52 B1-B2. In addition, we find that at least two flotillin-related genes are expressed in D. melanogaster. Our current results provide a starting point and systematic basis for dissecting the role of flotillin in caveolae and neuronal development using Drosophila as a genetic system.