Plasma membrane tension is an important feature that determines the cell shape and influences processes such as cell motility, spreading, endocytosis and exocytosis. Unconventional class 1 myosins are potent regulators of plasma membrane tension because they physically link the plasma membrane with adjacent cytoskeleton. We identified nuclear myosin 1 (NM1) - a putative nuclear isoform of myosin 1c (Myo1c) - as a new player in the field. Although having specific nuclear functions, NM1 localizes predominantly to the plasma membrane. Deletion of NM1 causes more than a 50% increase in the elasticity of the plasma membrane around the actin cytoskeleton as measured by atomic force microscopy. This higher elasticity of NM1 knock-out cells leads to 25% higher resistance to short-term hypotonic environment and rapid cell swelling. In contrast, overexpression of NM1 in wild type cells leads to an additional 30% reduction of their survival. We have shown that NM1 has a direct functional role in the cytoplasm as a dynamic linker between the cell membrane and the underlying cytoskeleton, regulating the degree of effective plasma membrane tension.

Department of Biology of the Cell Nucleus Institute of Molecular Genetics AS CR v v i Videnska 1083 142 20 Prague Czech Republic

Department of Biology of the Cell Nucleus Institute of Molecular Genetics AS CR v v i Videnska 1083 142 20 Prague Czech Republic Faculty of Science Charles University Prague Albertov 6 128 43 Prague Czech Republic

Department of Medical Biophysics Faculty of Medicine and Dentistry Palacky University in Olomouc Hnevotinska 3 775 15 Olomouc Czech Republic

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