Molecular cloning and characterization of profilin-3: A novel cytoskeleton-associated gene expressed in rat kidney and testes

Profilin is a small actin-binding protein that is involved in diverse funct ions such as maintaining cell structure integrity, cell mobility, tumor cel l metastasis, as well as growth factor signal transduction. In this paper, we describe the molecular cloning and characterization of a novel form of p rofilin, termed profilin-3, from rat kidney using a PCR-based procedure for isolating tissue-specific genes. The profilin-3 cDNA encoded 137 amino aci ds, and it shared extensive homology to profilin-1 and profilin-2 from mice and humans. More strikingly, the expression of profilin-3 was highly selec tive, and its mRNA was only found in the kidney and to a much lesser extent in the testis. The size of the mRNA for profilin-3 in the testis was 1.2 k b, while in kidney it was approximately 4.4-5 kb, suggesting the presence o f tissue-specific transcription from different promoters. In addition, we a lso found that the expression of profilin-3 mRNA was significantly elevated in two types of renal diseases: diabetic nephropathy (db/db mice) and poly cystic kidney diseases (cpk mice). Similar to profilin-l and profilin-2, pr ofilin-3 was localized in the cytoplasmic domain. Furthermore, it was capab le of interacting with actin and poly-L-proline in an in vitro assay as wel l as in transfected cells. These results strongly suggest that, contrary to the ubiguitous presence of profilin-1 and profilin-2, there is a tissue-sp ecific form of these cytoskeleton-regulatory proteins and that the kidney/t estes-specific profilin-3 may play a unique role in renal and/or reproducti ve functions. Copyright (C) 2001 S. Karger AG, Basel.