Subcellular Spatial Control of Non-Muscle Myosin 2 Redistribution and Stress Fiber Strain by Molecular Tattoo

Abstract

The cellular distribution of the motor protein non-muscle myosin 2 (NM2) leads to different forms of intracellular strain driving cell motility, cytokinesis and morphogenetic processes including axonal growth and retraction. However, it remains elusive how these cellular processes are governed by the dynamic changes in NM2 localization and supramolecular assembly. To address this problem, we determined the effect of different types of NM2 inhibition on the dynamics of load-bearing stress fibers and unloaded inner cytoplasmatic NM2 structures in live HeLa cells. We followed NM2 redistribution via FRAP, applied also in combination with our recently developed optopharmacological tool, Molecular Tattoo, which allows subcellular confinement of drug effects via 2-photon induced photocrosslinking to targets. We found that the Rho-kinase inhibitor, Y-27632, dramatically accelerates NM2 redistribution and induces stress fiber dissolution, due to NM2 filament disassembly resulting from myosin light chain dephosphorylation. When NM2 was inhibited by para-nitroblebbistatin (pNBleb) or locally by tattooed azidoblebbistatin, in the stress fibers a significant acceleration and suppression of NM2 redistribution was detected at moderate and high inhibitor concentrations, respectively. The observed effects were local and specific for load-bearing peripheral stress fibers, implying the role of mechanical load in NM2 redistribution. Furthermore, in these tests stress fibers remained intact, contrary to that seen upon Rho-kinase inhibition. These results highlight that variations in the localization and/or pharmacological mechanism of NM2 inhibition produce distinct effects on intracellular strain and cellular morphogenesis.Supported by Hungarian Research and Innovation Fund (VKSZ_14-1-2015-0052).