Flotillin-1: gene structure: cDNA cloning from human lung and the identification of alternative polyadenylation signals.

To identify changes in gene expression associated with emphysema, differential display was used to compare RNA extracted from emphysematous lung with that of unused donor tissue taken at the time of transplant. Two expressed clones with sequence homology to the 3' UTR of the murine flotillin-1 cDNA were identified. Flotillin-1 is a plasma membrane protein, which has been associated with detergent-insoluble glycolipid-rich domains and the formation of caveolae. One clone was 95 bp longer than the other. It arose from the use of a second polyadenylation signal and its existence was not due to differential expression nor to polymorphisms in the human flotillin-1 sequence. The 1839 bp human flotillin-1 sequence was completed by 5' RACE from a lung cDNA library. The human mRNA has a 1.9 kbase transcript being highly expressed in brain, heart and lung. The single copy flotillin-1 gene is located at 6p21.3 in the MHC class I region and consists of 13 exons over 15 kb. The ORF encodes a 427 residue protein with a molecular mass 47355 Da, and an isoelectric point 7.08. Human flotillin-1 has a 98% identity with the murine protein and a 47% identity with human flotillin-2. Flotillin-1 belongs to the Band 7.2/stomatin protein family, possessing a hydrophobic N-terminal region, predicted to form a single, outside to inside, transmembrane domain. The long central alpha-helical domain may form a coiled-coil. We have isolated and characterised a cDNA encoding the human flotillin-1 gene, which may play an important role in raft formation.