scholarly journals Mechanosensitive recruitment of stator units promotes binding of the response regulator CheY-P to the flagellar motor

2021 ◽  
Author(s):  
Jyot Antani ◽  
Rachit Gupta ◽  
Annie Lee ◽  
Kathy Rhee ◽  
Michael Manson ◽  
...  
Keyword(s):  
Adaptive Response ◽  
Mechanical Load ◽  
Response Regulator ◽  
Mechanical Stimulus ◽  
Viscous Resistance ◽  
Mechanical Forces ◽  
Mechanical Stimuli ◽  
Flagellar Motor ◽  
Neuromuscular Systems ◽  
Bacterial Flagellar Motor

Abstract Reversible switching of the bacterial flagellar motor between clockwise (CW) and counterclockwise (CCW) rotation is necessary for chemotaxis, which enables cells to swim towards favorable chemical habitats. Increase in the viscous resistance to the rotation of the motor (mechanical load) inhibits switching. However, cells must maintain homeostasis in switching to navigate within environments of different viscosities. The mechanism by which the cell maintains optimal chemotactic function under varying loads is not understood. Here, we show that the flagellar motor allosterically controls the binding affinity of the chemotaxis response regulator, CheY-P, to the flagellar switch complex by modulating the mechanical forces acting on the rotor. Mechanosensitive CheY-P binding compensates for the load-induced loss of switching by precisely adapting the switch response to a mechanical stimulus. The interplay between mechanical forces and CheY-P binding tunes the chemotactic function to match the load. This adaptive response of the chemotaxis output to mechanical stimuli resembles the proprioceptive feedback in the neuromuscular systems of insects and vertebrates.

scholarly journals Mechanosensitive recruitment of stator units promotes binding of the response regulator CheY-P to the flagellar motor

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jyot D. Antani ◽  
Rachit Gupta ◽  
Annie H. Lee ◽  
Kathy Y. Rhee ◽  
Michael D. Manson ◽  
...  
Keyword(s):  
Adaptive Response ◽  
Mechanical Load ◽  
Response Regulator ◽  
Mechanical Stimulus ◽  
Viscous Resistance ◽  
Mechanical Forces ◽  
Mechanical Stimuli ◽  
Flagellar Motor ◽  
Neuromuscular Systems ◽  
Bacterial Flagellar Motor

AbstractReversible switching of the bacterial flagellar motor between clockwise (CW) and counterclockwise (CCW) rotation is necessary for chemotaxis, which enables cells to swim towards favorable chemical habitats. Increase in the viscous resistance to the rotation of the motor (mechanical load) inhibits switching. However, cells must maintain homeostasis in switching to navigate within environments of different viscosities. The mechanism by which the cell maintains optimal chemotactic function under varying loads is not understood. Here, we show that the flagellar motor allosterically controls the binding affinity of the chemotaxis response regulator, CheY-P, to the flagellar switch complex by modulating the mechanical forces acting on the rotor. Mechanosensitive CheY-P binding compensates for the load-induced loss of switching by precisely adapting the switch response to a mechanical stimulus. The interplay between mechanical forces and CheY-P binding tunes the chemotactic function to match the load. This adaptive response of the chemotaxis output to mechanical stimuli resembles the proprioceptive feedback in the neuromuscular systems of insects and vertebrates.

scholarly journals Motile ghosts of the halophilic archaeon, Haloferax volcanii

2020 ◽  
Vol 117 (43) ◽  
pp. 26766-26772
Author(s):  
Yoshiaki Kinosita ◽  
Nagisa Mikami ◽  
Zhengqun Li ◽  
Frank Braun ◽  
Tessa E. F. Quax ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Atp Hydrolysis ◽  
Response Regulator ◽  
Model System ◽  
Flagellar Motor ◽  
Domains Of Life ◽  
Bacterial Flagellar Motor ◽  
Archaeal Flagellum ◽  
Triton Model ◽  
Rotary Motor

Archaea swim using the archaellum (archaeal flagellum), a reversible rotary motor consisting of a torque-generating motor and a helical filament, which acts as a propeller. Unlike the bacterial flagellar motor (BFM), ATP (adenosine-5′-triphosphate) hydrolysis probably drives both motor rotation and filamentous assembly in the archaellum. However, direct evidence is still lacking due to the lack of a versatile model system. Here, we present a membrane-permeabilized ghost system that enables the manipulation of intracellular contents, analogous to the triton model in eukaryotic flagella and gliding Mycoplasma. We observed high nucleotide selectivity for ATP driving motor rotation, negative cooperativity in ATP hydrolysis, and the energetic requirement for at least 12 ATP molecules to be hydrolyzed per revolution of the motor. The response regulator CheY increased motor switching from counterclockwise (CCW) to clockwise (CW) rotation. Finally, we constructed the torque–speed curve at various [ATP]s and discuss rotary models in which the archaellum has characteristics of both the BFM and F1-ATPase. Because archaea share similar cell division and chemotaxis machinery with other domains of life, our ghost model will be an important tool for the exploration of the universality, diversity, and evolution of biomolecular machinery.

scholarly journals Robustness in an Ultrasensitive Motor

mBio ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Guangzhe Liu ◽  
Antai Tao ◽  
Rongjing Zhang ◽  
Junhua Yuan
Keyword(s):  
Escherichia Coli ◽  
Response Regulator ◽  
Motor Output ◽  
Flagellar Motor ◽  
Content Type ◽  
P Concentration ◽  
Bacterial Flagellar Motor ◽  
Cell Variation

ABSTRACT In Escherichia coli, the chemotaxis response regulator CheY-P binds to FliM, a component of the switch complex at the base of the bacterial flagellar motor, to modulate the direction of motor rotation. The bacterial flagellar motor is ultrasensitive to the concentration of unbound CheY-P in the cytoplasm. CheY-P binds to FliM molecules both in the cytoplasm and on the motor. As the concentration of FliM unavoidably varies from cell to cell, leading to a variation of unbound CheY-P concentration in the cytoplasm, this raises the question whether the flagellar motor is robust against this variation, that is, whether the rotational bias of the motor is more or less constant as the concentration of FliM varies. Here, we showed that the motor is robust against variations of the concentration of FliM. We identified adaptive remodeling of the motor as the mechanism for this robustness. As the level of FliM molecules changes, resulting in different amounts of the unbound CheY-P molecules, the motor adaptively changes the composition of its switch complex to compensate for this effect. IMPORTANCE The bacterial flagellar motor is an ultrasensitive motor. Its output, the probability of the motor turning clockwise, depends sensitively on the occupancy of the protein FliM (a component on the switch complex of the motor) by the input CheY-P molecules. With a limited cellular pool of CheY-P molecules, cell-to-cell variation of the FliM level would lead to large unwanted variation of the motor output if not compensated. Here, we showed that the motor output is robust against the variation of FliM level and identified the adaptive remodeling of the motor switch complex as the mechanism for this robustness.

Loading-Induced Interstitial Fluid Flow in Bone Mechanobiology: An FSI Approach to the Osteocyte Environment

2012 ◽  
Author(s):  
Stefaan W. Verbruggen ◽  
Ted J. Vaughan ◽  
Laoise M. McNamara
Keyword(s):  
Adaptive Response ◽  
Interstitial Fluid ◽  
Bone Growth ◽  
Mechanical Stimulus ◽  
Mechanical Stimuli ◽  
Interstitial Fluid Flow ◽  
Physiological Demands ◽  
Control Bone ◽  
Ubiquitous Presence

Bone is an adaptive material, which is particularly responsive to mechanical loading and can adapt its mass and structure to meet the mechanical demands experienced throughout life. The osteocyte, due to its ubiquitous presence throughout bone, is believed to act as the main sensor of mechanical stimulus in bone, recruiting other cells to control bone growth and resorption in response to changes in physiological demands. However the precise mechanical stimuli that osteocytes experience in vivo, and what type of stimulus instigates an adaptive response, are not fully understood.

scholarly journals Load-Dependent Assembly of the Bacterial Flagellar Motor

mBio ◽  
2013 ◽  
Vol 4 (4) ◽  
Author(s):  
Murray J. Tipping ◽  
Nicolas J. Delalez ◽  
Ren Lim ◽  
Richard M. Berry ◽  
Judith P. Armitage
Keyword(s):  
External Load ◽  
Mechanical Load ◽  
Life Cycles ◽  
High Load ◽  
Solid Surfaces ◽  
Flagellar Motor ◽  
Essential Factor ◽  
Liquid Media ◽  
External Mechanical Load ◽  
Bacterial Flagellar Motor

ABSTRACTIt is becoming clear that the bacterial flagellar motor output is important not only for bacterial locomotion but also for mediating the transition from liquid to surface living. The output of the flagellar motor changes with the mechanical load placed on it by the external environment: at a higher load, the motor runs more slowly and produces higher torque. Here we show that the number of torque-generating units bound to the flagellar motor also depends on the external mechanical load, with fewer stators at lower loads. Stalled motors contained at least as many stators as rotating motors at high load, indicating that rotation is unnecessary for stator binding. Mutant stators incapable of generating torque could not be detected around the motor. We speculate that a component of the bacterial flagellar motor senses external load and mediates the strength of stator binding to the rest of the motor.IMPORTANCEThe transition between liquid living and surface living is important in the life cycles of many bacteria. In this paper, we describe how the flagellar motor, used by bacteria for locomotion through liquid media and across solid surfaces, is capable of adjusting the number of bound stator units to better suit the external load conditions. By stalling motors using external magnetic fields, we also show that rotation is not required for maintenance of stators around the motor; instead, torque production is the essential factor for motor stability. These new results, in addition to previous data, lead us to hypothesize that the motor stators function as mechanosensors as well as functioning as torque-generating units.

scholarly journals Motile ghosts of the halophilic archaeon, Haloferax volcanii

2020 ◽  
Author(s):  
Yoshiaki Kinosita ◽  
Nagisa Mikami ◽  
Zhengqun Li ◽  
Frank Braun ◽  
Tessa EF. Quax ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Atp Hydrolysis ◽  
Response Regulator ◽  
Model System ◽  
Flagellar Motor ◽  
Domains Of Life ◽  
Bacterial Flagellar Motor ◽  
Archaeal Flagellum ◽  
Triton Model ◽  
Rotary Motor

SummaryMotility is seen across all domains of life1. Prokaryotes exhibit various types of motilities, such as gliding, swimming, and twitching, driven by supramolecular motility machinery composed of multiple different proteins2. In archaea only swimming motility is reported, driven by the archaellum (archaeal flagellum), a reversible rotary motor consisting of a torque-generating motor and a helical filament which acts as a propeller3,4. Unlike the bacterial flagellar motor (BFM), adenosine triphosphate (ATP) hydrolysis probably drives both motor rotation and filamentous assembly in the archaellum5,6. However, direct evidence is still lacking due to the lack of a versatile model system. Here we present a membrane-permeabilized ghost system that enables the manipulation of intracellular contents, analogous to the triton model in eukaryotic flagella7 and gliding Mycoplasma8,9. We observed high nucleotide selectivity for ATP driving motor rotation, negative cooperativity in ATP hydrolysis and the energetic requirement for at least 12 ATP molecules to be hydrolyzed per revolution of the motor. The response regulator CheY increased motor switching from counterclockwise (CCW) to clockwise (CW) rotation, which is the opposite of a previous report10. Finally, we constructed the torque-speed curve at various [ATP]s and discuss rotary models in which the archaellum has characteristics of both the BFM and F1-ATPase. Because archaea share similar cell division and chemotaxis machinery with other domains of life11,12, our ghost model will be an important tool for the exploration of the universality, diversity, and evolution of biomolecular machinery.

scholarly journals CapZ integrates several signaling pathways in response to mechanical stiffness

2019 ◽  
Vol 151 (5) ◽  
pp. 660-669 ◽  
Author(s):  
Christopher Solís ◽  
Brenda Russell
Keyword(s):  
Mechanical Load ◽  
Phosphorylation Site ◽  
Tight Binding ◽  
Neonatal Rat ◽  
Actin Binding ◽  
Mechanical Stimuli ◽  
Muscle Adaptation ◽  
Capping Protein ◽  
Actin Capping Protein ◽  
Actin Capping

Muscle adaptation is a response to physiological demand elicited by changes in mechanical load, hormones, or metabolic stress. Cytoskeletal remodeling processes in many cell types are thought to be primarily regulated by thin filament formation due to actin-binding accessory proteins, such as the actin-capping protein. Here, we hypothesize that in muscle, the actin-capping protein (named CapZ) integrates signaling by a variety of pathways, including phosphorylation and phosphatidylinositol 4,5-bisphosphate (PIP2) binding, to regulate muscle fiber growth in response to mechanical load. To test this hypothesis, we assess mechanotransduction signaling that regulates muscle growth using neonatal rat ventricular myocytes cultured on substrates with the stiffness of the healthy myocardium (10 kPa), fibrotic myocardium (100 kPa), or glass. We investigate how PIP2 signaling affects CapZ using the PIP2 sequestering agent neomycin and the effect of PKC-mediated CapZ phosphorylation using the PKC-activating drug phorbol 12-myristate 13-acetate (PMA). Molecular simulations suggest that close interactions between PIP2 and the β-tentacle of CapZ are modified by phosphorylation at T267. Fluorescence recovery after photobleaching (FRAP) demonstrates that the kinetic binding constant of CapZ to sarcomeric thin filaments in living muscle cells increases with stiffness or PMA treatment but is diminished by PIP2 reduction. Furthermore, CapZ with a deletion of the β-tentacle that lacks the phosphorylation site T267 shows increased FRAP kinetics with lack of sensitivity to PMA treatment or PIP2 reduction. Förster resonance energy transfer (FRET) probes the molecular interactions between PIP2 and CapZ, which are decreased by PIP2 availability or by the β-tentacle truncation. These data suggest that CapZ is bound to actin tightly in the idle, locked state, with little phosphorylation or PIP2 binding. However, this tight binding is loosened in growth states triggered by mechanical stimuli such as substrate stiffness, which may have relevance to fibrotic heart disease.

The initiation of nerve impulses by mesenteric Pacinian corpuscles

1950 ◽  
Vol 137 (886) ◽  
pp. 96-114 ◽  
Keyword(s):  
Conditioning Stimulus ◽  
Mechanical Stimulus ◽  
Constant Current ◽  
Mechanical Stimuli ◽  
Pacinian Corpuscles ◽  
Nerve Impulses ◽  
A Value ◽  
Test Shock ◽  
Long Duration ◽  
Refractory State

A preparation of a single Pacinian corpuscle in the cat’s mesentery has been used to study the initiation of nerve impulses in sensory endings. The minimum movement of a mechanical stimulator required to excite a single corpuscle has been found to be 0⋅5 μ in 100 μ sec. It has been difficult to produce repetitive discharges with rectangular pulses of long duration, either mechanical or of constant current. The latency between a mechanical stimulus and the initiation of an impulse has a value around 1⋅5 msec, for threshold stimuli, and this decreases to a minimum value around 0⋅5 msec, as the stimulus is increased; it is altered only slightly, if at all, by changes in the duration of the maintained displacement of the mechanical stimulator. Subthreshold mechanical stimuli have been shown to facilitate stimulation by electrical test shocks. The return of excitability at the ending is independent of the nature of the conditioning stimulus and varies but little with the nature of the test shock. The value of the latency at threshold is unaffected by the relatively refractory state. The relations of these results to various hypotheses are discussed, and it is suggested that these results can all be accounted for in terms of the known properties of axons.

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