Refilin holds the cap.

The Refilins (RefilinA and RefilinB) are a novel family of short-lived actin regulatory proteins that are expressed during changes in cellular phenotype such as epithelial to mesenchymal transition (EMT). The Refilins promote the formation of actin- and myosin-rich perinuclear bundles that are characteristic of cellular phenotypic switches. In epithelial cells, RefilinB is upregulated in response to TGFβ stimulation and functions in organization of apical perinuclear actin fibers during early stage of the EMT process. In fibroblasts, RefilinB stabilizes perinuclear parallel actin bundles which resemble actin cap. Refilins bind and modulate the function of Filamin A (FLNA). Upon binding to Refilins, FLNA is capable of assembling actin filaments into parallel bundles, possibly by undergoing conformational changes at the C-terminal. Perinuclear actin structures determine nuclear shape, cell morphology, cell adhesion and possibly cell proliferation and gene regulation. Identifying the role of Refilins in organizing perinuclear actin networks provides additional insight in the process of intracellular mechanotransduction that regulate changes in cellular phenotype such as those observed during EMT. [ABSTRACT FROM AUTHOR]