Evidence for an electrogenic ion transport pump in cells of higher plants

In the present work, we compared the outcome of hyperosmotic and isosmotic shrinkage on ion transport and protein phosphorylation in C11-MDCK cells resembling intercalated cells from collecting ducts and in vascular smooth muscle cells (VSMC) from the rat aorta. Hyperosmotic shrinkage was triggered by cell exposure to hypertonic medium, whereas isosmotic shrinkage was evoked by cell transfer from an hypoosmotic to an isosmotic environment. Despite a similar cell volume decrease of 40%–50%, the consequences of hyperosmotic and isosmotic shrinkage on cellular functions were sharply different. In C11-MDCK and VSMC, hyperosmotic shrinkage completely inhibited Na+,K+-ATPase and Na+,Pi cotransport. In contrast, in both types of cells isosmotic shrinkage slightly increased rather than suppressed Na+,K+-ATPase and did not change Na+,Pi cotransport. In C11-MDCK cells, phosphorylation of JNK1/2 and Erk1/2 mitogen-activated protein kinases was augmented in hyperosmotically shrunken cells by ∼7- and 2-fold, respectively, but was not affected in cells subjected to isosmotic shrinkage. These results demonstrate that the data obtained in cells subjected to hyperosmotic shrinkage cannot be considered as sufficient proof implicating cell volume perturbations in the regulation of cellular functions under isosmotic conditions.

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Elementary auxin response chains at the plasma membrane involve external abp1 and multiple electrogenic ion transport proteins

Plant Growth Regulation ◽

10.1007/bf00028484 ◽

1996 ◽

Vol 18 (1-2) ◽

pp. 23-28 ◽

Cited By ~ 11

Author(s):

H�l�ne Barbier-Brygoo ◽

Sabine Zimmermann ◽

S�bastien Thomine ◽

Ian R. White ◽

Paul Millner ◽

...

Keyword(s):

Plasma Membrane ◽

Ion Transport ◽

Transport Proteins ◽

Auxin Response ◽

Electrogenic Ion Transport ◽

Response Chains

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PHYSIOLOGY OF ION TRANSPORT ACROSS THE TONOPLAST OF HIGHER PLANTS

Annual Review of Plant Physiology and Plant Molecular Biology ◽

10.1146/annurev.arplant.47.1.159 ◽

1996 ◽

Vol 47 (1) ◽

pp. 159-184 ◽

Cited By ~ 91

Author(s):

Bronwyn J. Barkla ◽

Omar Pantoja

Keyword(s):

Ion Transport ◽

Higher Plants

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ATP Levels and Energy Requirements of Ion Transport in Cells of Slices of Greening Barley Leaves

Zeitschrift für Pflanzenphysiologie ◽

10.1016/s0044-328x(76)80050-5 ◽

1976 ◽

Vol 80 (1) ◽

pp. 50-59 ◽

Cited By ~ 9

Author(s):

Ulrich Lüttge ◽

Erika Ball

Keyword(s):

Ion Transport ◽

Energy Requirements ◽

Atp Levels ◽

Barley Leaves ◽

In Cells

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Enterohemorrhagic E. coli (EHEC)—Secreted Serine Protease EspP Stimulates Electrogenic Ion Transport in Human Colonoid Monolayers

Toxins ◽

10.3390/toxins10090351 ◽

2018 ◽

Vol 10 (9) ◽

pp. 351 ◽

Cited By ~ 3

Author(s):

C. Tse ◽

Julie In ◽

Jianyi Yin ◽

Mark Donowitz ◽

Michele Doucet ◽

...

Keyword(s):

Ion Transport ◽

Serine Protease ◽

Shiga Toxin ◽

Short Circuit ◽

Ussing Chamber ◽

Adult Stem Cell ◽

Short Circuit Current ◽

Watery Diarrhea ◽

E Coli ◽

Electrogenic Ion Transport

One of the characteristic manifestations of Shiga-toxin-producing Escherichia coli (E. coli) infection in humans, including EHEC and Enteroaggregative E. coli O104:H4, is watery diarrhea. However, neither Shiga toxin nor numerous components of the type-3 secretion system have been found to independently elicit fluid secretion. We used the adult stem-cell-derived human colonoid monolayers (HCM) to test whether EHEC-secreted extracellular serine protease P (EspP), a member of the serine protease family broadly expressed by diarrheagenic E. coli can act as an enterotoxin. We applied the Ussing chamber/voltage clamp technique to determine whether EspP stimulates electrogenic ion transport indicated by a change in short-circuit current (Isc). EspP stimulates Isc in HCM. The EspP-stimulated Isc does not require protease activity, is not cystic fibrosis transmembrane conductance regulator (CFTR)-mediated, but is partially Ca2+-dependent. EspP neutralization with a specific antibody reduces its potency in stimulating Isc. Serine Protease A, secreted by Enteroaggregative E. coli, also stimulates Isc in HCM, but this current is CFTR-dependent. In conclusion, EspP stimulates colonic CFTR-independent active ion transport and may be involved in the pathophysiology of EHEC diarrhea. Serine protease toxins from E. coli pathogens appear to serve as enterotoxins, potentially significantly contributing to watery diarrhea.

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