Coronin proteins as multifunctional regulators of the cytoskeleton and membrane trafficking

Coronins constitute an evolutionarily conserved family of WD-repeat actin-binding proteins, which can be clearly classified into two distinct groups based on their structural features. All coronins possess a conserved basic N-terminal motif and three to ten WD repeats clustered in one or two core domains. Dictyostelium and mammalian coronins are important regulators of the actin cytoskeleton, while the fly Dpod1 and the yeast coronin proteins crosslink both actin and microtubules. Apart from that, several coronins have been shown to be involved in vesicular transport. C. elegans POD-1 and Drosophila coro regulate the actin cytoskeleton, but also govern vesicular trafficking as indicated by mutant phenotypes. In both organisms, defects in cytoskeleton and trafficking lead to severe developmental defects ranging from abnormal cell division to aberrant formation of morphogen gradients. Finally, mammalian coronin 7 appears not to execute any cytoskeleton-related functions, but rather participates in regulating Golgi trafficking. Here, we review recent data providing more insight into molecular mechanisms underlying the regulation of F-actin structures, cytoskeletal rearrangements and intracellular membrane transport by coronin proteins and the way that they might link cytoskeleton with trafficking in development and disease.