Tunable Cellular Localization and Extensive Cytoskeleton-Interplay of Reflectins

Abstract

Reflectins are membrane-bound proteins located in cephalopods iridocytes, with repeated canonical domains interspersed with cationic linkers. Scientists keep curious about their evolutionary processes, biochemical properties and intracellular functions. Here, by introducing reflectin A1, A2, B1 and C into HEK-293T cells, these proteins were found to phase out from the crowded intracellular milieu, with distinguished localization preferences. Inspired by their programmable block sequences, several truncated reflectin A1 (RfA1) peptides based on repetition of reflectin motifs were designed and transfected into cells. An obvious cyto-/nucleo-plasmic localization preference was once again observed. The dynamic performance of RfA1 derivatives and their analogic behavior between different reflectins suggest a conceivable evolutionary relationship among reflectin proteins. Additionally, a proteomic survey identified biochemical partners which contribute to the phase separation and intracellular localization of RfA1 and its truncations, as well as the close collaboration between RfA1 and the cytoskeleton systems. These findings indicate that liquid-liquid phase separation could be the fundamental mode for reflectins to achieve spatial organization, to cooperate with cytoskeleton during the regulation of reflective coloration. On the other hand, the dynamic behaviors of RfA1 derivatives strongly recommended themselves as programmable molecular tools.