A novel muscle LIM-only protein is generated from the paxillin gene locus in Drosophila

Paxillin is a protein containing four LIM domains, and functions in integri n signaling. We report here that two transcripts are generated from the pax illin gene locus in Drosophila; one encodes a protein homolog of the verteb rate Paxillin (DPxn37), and the other a protein with only three LIM domains , partly encoded by its own specific exon (PDLP). At the myotendinous junct ions of Drosophila embryos where integrins play important roles, both DPxn3 7 and PDLP are highly expressed with different patterns; DPxn37 is predomin antly concentrated at the center of the junctions, whereas PDLP is highly e nriched at neighboring sides of the junction centers, primarily expressed i n the mesodermal myotubes. Northern blot analysis revealed that DPxn37 is u biquitously expressed throughout the life cycle, whereas PDLP expression ex hibits a biphasic pattern during development, largely concomitant with musc le generation and remodeling. Our results collectively reveal that a unique system exists in Drosophila for the generation of a novel type of LIM-only protein, highly expressed in the embryonic musclature, largely utilizing t he Paxillin LIM domains.