Expression profiling of NM1 KO and WT mice. Mus musculus

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 the 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 function, we show that NM1 localizes preferentially to the plasma membrane. Deletion of NM1 causes more than 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 contrary, overexpression of NM1 in WT cells leads to additional 30% reduction of their survival. We have brought evidence 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. Overall design: We used tissues from NM1 WT and KO mice with highest expression of NM1, lungs and heart (3 replicates each) and skin fibroblast derived from each mice (2 replicates each)