Challenge Integrity: The Cell-Penetrating Peptide BP100 Interferes with the Auxin-Actin Oscillator.
Actin filaments are essential for the integrity of the cell membrane. In addition to this structural role, actin can modulate signaling by altering polar auxin flow. On the other hand, the organization of actin filaments is modulated by auxin constituting a self-referring signaling hub. Although the function of this auxin–actin oscillator is not clear, there is evidence for a functional link with stress signaling activated by the NADPH oxidase Respiratory burst oxidase Homolog (RboH). In the current work, we used the cell-penetrating peptide BP100 to induce a mild and transient perturbation of membrane integrity. We followed the response of actin to the BP100 uptake in a green fluorescent protein (GFP)-tagged actin marker line of tobacco Bright Yellow 2 (BY-2) cells by spinning disc confocal microscopy. We observed that BP100 enters in a stepwise manner and reduces the extent of actin remodeling. This actin ‘freezing’ can be rescued by the natural auxin IAA, and mimicked by the auxin-efflux inhibitor 1-napthylphthalamic acid (NPA). We further tested the role of the membrane-localized NADPH oxidase RboH using the specific inhibitor diphenyl iodonium (DPI), and found that DPI acts antagonistically to BP100, although DPI alone can induce a similar actin ‘freezing’ as well. We propose a working model, where the mild violation of membrane integrity by BP100 stimulates RboH, and the resulting elevated levels of reactive oxygen species interfere with actin dynamicity. The mitigating effect of auxin is explained by competition of auxin- and RboH-triggered signaling for superoxide anions. This self-referring auxin–actin–RboH hub might be essential for integrity sensing.
Botanical Institute and DFG-Center of Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Kaiserstr, Karlsruhe, Germany.
Kai
K
Eggenberger
Institute of Biological Interfaces (IBG-2) and DFG-Center of Functional Nanostructures (CFN), Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT), Fritz-Haber Weg 6, Karlsruhe, Germany.
Papia
P
Sanyal
Botanical Institute and DFG-Center of Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Kaiserstr, Karlsruhe, Germany.
Svenja
S
Hundt
Institute of Biological Interfaces (IBG-2) and DFG-Center of Functional Nanostructures (CFN), Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT), Fritz-Haber Weg 6, Karlsruhe, Germany.
Parvesh
P
Wadhwani
Institute of Biological Interfaces (IBG-2) and DFG-Center of Functional Nanostructures (CFN), Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT), Fritz-Haber Weg 6, Karlsruhe, Germany.
Anne S
AS
Ulrich
Botanical Institute and DFG-Center of Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Kaiserstr, Karlsruhe, Germany.
Peter
P
Nick
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D057846:Cell-Penetrating Peptides / Q000494:pharmacology*; D005615:Freezing; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D008954:Models, Biological; D009842:Oligopeptides / Q000494:pharmacology*; D009861:Onium Compounds / Q000494:pharmacology; D014026:Nicotiana / Q000187:drug effects / Q000378:metabolism
D000199:Actins; D057846:Cell-Penetrating Peptides; D007210:Indoleacetic Acids; D009842:Oligopeptides; D009861:Onium Compounds; C540525:lysyl-lysyl-leucyl-phenylalanyl-lysyl-lysyl-isoleucyl-leucyl-lysyl-tyrosyl-leucinamide; D049452:Green Fluorescent Proteins; C007517:diphenyleneiodonium
Actin; Auxin; BP100; Respiratory burst oxidase Homolog (RboH); Tobacco (Nicotiana tabacum L.) BY-2