Multiple myosin motors interact with sodium/potassium-ATPase alpha 1 subunits

Bhagirathi Dash,Sulayman D Dib-Hajj,Stephen G Waxman

doi:10.1186/s13041-018-0388-1

Bhagirathi Dash, Sulayman D Dib-Hajj + Show 1 more

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https://doi.org/10.1186/s13041-018-0388-1

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Journal: Molecular brain	Publication Date: Aug 7, 2018
Citations: 11	License type: open-access

Affiliation: Yale University, VA Connecticut Healthcare System

Abstract

The alpha1 (α1) subunit of the sodium/potassium ATPase (i.e., Na+/K+-ATPase α1), the prototypical sodium pump, is expressed in each eukaryotic cell. They pump out three sodium ions in exchange for two extracellular potassium ions to establish a cellular electrochemical gradient important for firing of neuronal and cardiac action potentials. We hypothesized that myosin (myo or myh) motor proteins might interact with Na+/K+-ATPase α1 subunits in order for them to play an important role in the transport and trafficking of sodium pump. To this end immunoassays were performed to determine whether class II non-muscle myosins (i.e., NMHC-IIA/myh9, NMHC-IIB/myh10 or NMHC-IIC/myh14), myosin Va (myoVa) and myosin VI (myoVI) would interact with Na+/K+-ATPase α1 subunits. Immunoprecipitation of myh9, myh10, myh14, myoVa and myoVI from rat brain tissues led to the co-immunoprecipitation of Na+/K+-ATPase α1 subunits expressed there. Heterologous expression studies using HEK293 cells indicated that recombinant myh9, myh10, myh14 and myoVI interact with Na+/K+-ATPase α1 subunits expressed in HEK293 cells. Additional results indicated that loss of tail regions in recombinant myh9, myh10, myh14 and myoVI did not affect their interaction with Na+/K+-ATPase α1 subunits. However, recombinant myh9, myh10 and myh14 mutants having reduced or no actin binding ability, as a result of loss of their actin binding sites, displayed greatly reduced or null interaction with Na+/K+-ATPase α1 subunits. These results suggested the involvement of the actin binding site, but not tail regions, of NMHC-IIs in their interaction with Na+/K+-ATPase α1 subunits. Overall these results suggest a role for these diverse myosins in the trafficking and transport of sodium pump in neuronal and non-neuronal tissues.

Highlights

The sodium pump is an integral membrane protein found in the cells of all higher eukaryotes [1]
We assessed the ability of myh14, myosin Va (myoVa) and myosin VI (myoVI) to immunoprecipitate their respective cognate antigens and/or co-immunoprecipitate β-actin (Figs. 1b and 4). β-actin was co-immunoprecipitated with myh14, myoVa and myoVI to various degrees from rodent brain tissues (Fig. 1)
In this work we show that all the three non-muscle myosin heavy chain (NMHC)-IIs interact with Na+/K+-ATPase α1 subunits expressed in the rodent brain and HEK293 cells (Table 1)

Summary

Introduction

The sodium pump (sodium/potassium ATPase; Na+/ K+-ATPase) is an integral membrane protein found in the cells of all higher eukaryotes [1]. It utilizes ATP as a driving force to pump out three sodium ions in exchange for two extracellular potassium ions which establishes both a chemical and an electrical gradient across the cell membrane. The electrical gradient is essential for maintaining cellular resting potential and excitability of myocytes (skeletal and cardiac) and neurons. The sodium gradient helps drive various transport processes such as the fluid reabsorption and translocation of glucose, amino acids, Dash et al Molecular Brain (2018) 11:45 muscle, heart, and brain (i.e., mostly glial cells). The α3 subunits are abundant in nervous tissues (i.e., mostly neurons). Ablation of Na+/K+-ATPase α1, α2 or α3 subunits result in the death of the animal [7]

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