Phospho-regulation of tropomyosin is crucial for actin cable turnover and division site placement.

November 13, 2019

Title

Phospho-regulation of tropomyosin is crucial for actin cable turnover and division site placement.

Author

Saravanan Palani, Darius V. Köster, Tomoyuki Hatano, Anton Kamnev, Taishi Kanamaru, Holly R. Brooker, Juan Ramon Hernandez-Fernaud, Alexandra M.E. Jones, Jonathan B.A. Millar, Daniel P. Mulvihill, Mohan K. Balasubramanian

Year

2019

Journal

Journal of Cell Biology

Abstract

Tropomyosin is a coiled-coil actin binding protein key to the stability of actin filaments. In muscle cells, tropomyosin is subject to calcium regulation, but its regulation in nonmuscle cells is not understood. Here, we provide evidence that the fission yeast tropomyosin, Cdc8, is regulated by phosphorylation of a serine residue. Failure of phosphorylation leads to an increased number and stability of actin cables and causes misplacement of the division site in certain genetic backgrounds. Phosphorylation of Cdc8 weakens its interaction with actin filaments. Furthermore, we show through in vitro reconstitution that phosphorylation-mediated release of Cdc8 from actin filaments facilitates access of the actin-severing protein Adf1 and subsequent filament disassembly. These studies establish that phosphorylation may be a key mode of regulation of nonmuscle tropomyosins, which in fission yeast controls actin filament stability and division site placement.

Instrument

J-715

Keywords

Circular dichroism, Secondary structure, Thermal stability, Biochemistry