SEPTINS MAY FORM A UBIQUITOUS FAMILY OF CYTOSKELETAL FILAMENTS

THIS minireview discusses recent information about the septin family o f proteins, which suggests that the septins may be elements of a new f ilament system that functions in all or most eukaryotic cells. Septins are found in a wide variety of eukaryotes, are important for cytokine sis, and may compose or regulate a ubiquitous filament system that has not been previously recognized. A more extensive review of septins wa s recently published (26). This minireview also presents a new compari son of septin sequences. Actin filaments, microtubules, intermediate f ilaments, and myosin thick filaments, have been extensively studied ov er the past several decades, using methodologic advances in electron a nd light microscopy, detergent extraction of cells, and purification o f proteins. This collection of filaments has been assumed to represent a fairly complete picture of the cytoskeletal filaments commonly foun d in eukaryotes. However, recent work suggests that cells augment thes e common cytoskeletal elements with additional elements, at least one of which, the septins, appears to be widely expressed and used for ess ential cell processes.