Caprice/MISP is a novel F-actin bundling protein critical for actin-based cytoskeletal reorganizations

Caprice [C19orf21 actin-bundling protein in characteristic epithelial cells, also called mitotic interactor and substrate of Plk1 (MISP)] is a novel actin-related protein identified in the highly-insoluble subcellular scaffold proteins. This protein contains multiple actin-binding sites, forms characteristic mesh-like F-actin bundles in vitro, and exhibits capricious localization and expression patterns in vivo. Overexpression or knock-down of Caprice resulted in a dramatic effect on cellular morphology by inducing stress fiber-like thick filaments or filopodial formations, respectively. Caprice is expressed and localized in distinct cells and tissues with specialized actin-based structures, such as growth cones of migrating neurons and stereocilia of inner ear hair cells. However, Caprice gene expression is varied among different cell types; especially enriched in several epithelial cells whereas relatively suppressed in a subset of epithelial cells, fibroblasts, and neuroblastoma cells at the transcriptional level. Thus, this protein is expected to be an effector for cell type-specific actin reorganization with its direct actin-binding properties and provides a novel model of cell morphology regulation by a non-ubiquitous single actin-bundling protein.