Coexpression of alpha 1 with putative beta 3 subunits results in functional Na+/K+ pumps in Xenopus oocytes.

Horisberger, Jean‐Daniel; Jaunin, Philippe; Good, Peter J.; Rossier, Bernard C.; Geering, K.

doi:10.1073/pnas.88.19.8397

Cited by 57 publications

(45 citation statements)

References 22 publications

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“…For the first time, we have measured the voltage dependence of Na,K-ATPase isozymes expressed in the same experimental system and we show that voltage-dependence is influenced by the ␣ isoform present in the Na,K-pump. In the presence of external Na ϩ and saturating concentrations of K ϩ , the profile of the I-V curve obtained for human ␣1-␤1 complexes is similar to that previously reported for Xenopus ␣1-␤1 (38). In comparison, human ␣2-␤1 complexes show a steeper voltage dependence while ␣3-␤1 complexes are nearly voltage-independent over the whole potential range.…”

Section: Nak-atpase Isozymessupporting

confidence: 66%

Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes

Crambert¹,

Hasler²,

Beggah³

et al. 2000

Journal of Biological Chemistry

395

378

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Na,K-ATPase plays a crucial role in cellular ion homeostasis and is the pharmacological receptor for digitalis in man. Nine different human Na,K-ATPase isozymes, composed of 3 ␣ and ␤ isoforms, were expressed in Xenopus oocytes and were analyzed for their transport and pharmacological properties. According to ouabain binding and K ؉ -activated pump current measurements, all human isozymes are functional but differ in their turnover rates depending on the ␣ isoform. On the other hand, variations in external K ؉ activation are determined by a cooperative interaction mechanism between ␣ and ␤ isoforms with ␣2-␤2 complexes having the lowest apparent K ؉ affinity. ␣ Isoforms influence the apparent internal Na ؉ affinity in the order ␣1 > ␣2 > ␣3 and the voltage dependence in the order ␣2 > ␣1 > ␣3. All human Na,K-ATPase isozymes have a similar, high affinity for ouabain. However, ␣2-␤ isozymes exhibit more rapid ouabain association as well as dissociation rate constants than ␣1-␤ and ␣3-␤ isozymes. Finally, isoformspecific differences exist in the K ؉ /ouabain antagonism which may protect ␣1 but not ␣2 or ␣3 from digitalis inhibition at physiological K ؉ levels. In conclusion, our study reveals several new functional characteristics of human Na,K-ATPase isozymes which help to better understand their role in ion homeostasis in different tissues and in digitalis action and toxicity.

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Section: Nak-atpase Isozymessupporting

confidence: 66%

Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes

Crambert¹,

Hasler²,

Beggah³

et al. 2000

Journal of Biological Chemistry

395

378

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“…This possiblity is also supported by the finding that the /I-subunit of (H,K)ATPase, the sequence of which in this loop is quite different from that of the B-subunit of (H,K)ATPase, forms a stable complex with the c+subunit of (Na,K)ATPase, but this hybrid is catalytically inactive [34]. (It is to be noted that this hybrid exhibits a low pump activity according to Horisberger et al [33]). Probably a specific sequence in the C~S'~~-C~S"~ loop in the (Na,K)ATPase /Y-subunit is required for the functional assembly of the (Na,K)ATPase 01-and B-subunits.…”

Section: Discussionsupporting

confidence: 53%

“…"', Glya9, TY?~~, Pro259, Leu260 and Asn267) are not only conserved among/I1 and 82 isoforms of the (Na,K)ATPase /9-subunit [26,27] but are also identical to the corresponding residues of the B-subunit of (H,K)ATPase [28][29][30][31][32]. The /?-subunit of (H,K)ATPase has been shown to assemble with the a-subunit of (Na,K)ATPase to form a stable, trypsin-resistant @-complex [33,34], probably because of the similarity of the sequences of the Cysr6'-CYS'~~ and Cys 215-Cys278 loops between the B-subunits of the two ATPases. On the other hand, the sequence of the cys'*7-cys 150 loop of isoform Bl is only 33% conserved among the species examined and there is only one residue (Lys14') that is identical in the @.tbunit (/31 and 82) of (Na,K)ATPase and the B-subunit of (H,K)ATPase.…”

Section: Discussionmentioning

confidence: 99%

The functional roles of disulfide bonds in the β‐subunit of (Na,K)ATPase as studied by site‐directed mutagenesis

1994

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The /I-subunit of Torpedo californica (Na,K)ATPase contains seven cysteine residues; one (Cysti) is in the single transmembrane segment and the other six (CYS'*~, Cys'%, Cys'@', CYS'~~, Cys"' and Cysz7*) are in the extracellular domain and form three highly conserved disulfide bonds. A/?-subunit mutant with replacement of Cy@ by Ser could assemble with the a-subunit, and the resulting a&complex was catalytically active. Mutants in which either the N-terminal side or both Cys residues of the Cys"%ys Iso bond were replaced by Ser could also tightly assemble with the a-subunit, but the resulting @complex was catalytically inactive. On the other hand, disruption of either the Cy~'~-Cys'~~ or Cy~~'~-Cys~~s bond by substituting the N-terminal side only or both Cys residues with Ser led to aSsubunit that could not assemble with the u-subunit. We conclude that the structure of the @ubunit around the Cy~'~Cys'~~ and Cy~~'~-Cys 27* loops is indispensable for assembly with the u-subunit, whereas the Cy~'~~-Cys'~~ loop is not essential for assembly but is required for enzyme activity.

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“…I p in the same experiment in control cells (without aldosterone and MEK1/2 inhibitors treatment) is shown as a dotted curve. D, Na,K-pump current (I p ) was measured as described earlier (40). U0126 was added for 4 min at a concentration of 50 M. Na,K-pump inhibition by 10 M ouabain was measured at the end.…”

Section: Pd98059 Reversibly Inhibits Transepithelial Sodium Transportmentioning

confidence: 99%

ERK1/2 Controls Na,K-ATPase Activity and Transepithelial Sodium Transport in the Principal Cell of the Cortical Collecting Duct of the Mouse Kidney

Michlig

Mercier

Doucet

et al. 2004

Journal of Biological Chemistry

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The collecting duct of normal kidney exhibits significant activity of the MEK1/2-ERK1/2 pathway as shown in vivo by immunostaining of phosphorylated active ERK1/2 (pERK1/2). The MEK1/2-ERK1/2 pathway controls many different ion transports both in proximal and distal nephron, raising the question of whether this pathway is involved in the basal and/or hormone-dependent transepithelial sodium reabsorption in the principal cell of the cortical collecting duct (CCD), a process mediated by the apical epithelial sodium channel and the basolateral sodium pump (Na,K-ATPase). To answer this question we used ex vivo microdissected CCDs from normal mouse kidney or in vitro cultured mpkCCD cl4 principal cells. Significant basal levels of pERK1/2 were observed ex vivo and in vitro. Aldosterone and vasopressin, known to up-regulate sodium reabsorption in CCDs, did not change ERK1/2 activity either ex vivo or in vitro. Basal and aldosterone-or vasopressin-stimulated sodium transport was down-regulated by the MEK1/2 inhibitor PD98059, in parallel with a decrease in pERK1/2 in vitro. The activity of Na,K-ATPase but not that of epithelial sodium channel was inhibited by MEK1/2 inhibitors in both unstimulated and aldosterone-or vasopressin-stimulated CCDs in vitro. Cell surface biotinylation showed that intrinsic activity rather than cell surface expression of Na,K-ATPase was controlled by pERK1/2. PD98059 also significantly inhibited the activity of Na,K-ATPase ex vivo. Our data demonstrate that the ERK1/2 pathway controls Na,K-ATPase activity and transepithelial sodium transport in the principal cell and indicate that basal constitutive activity of the ERK1/2 pathway is a critical component of this control.The extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) 1 pathway, also known as p42 and p44 mitogen-activated protein (MAP) kinase pathway, plays a critical role in cellular responses to a wide variety of external stimuli including hormones, growth factors, and environmental stress (for review, see Refs. 1 and 2). The ERK1/2 pathway is a three-step kinase cascade in which ERK1/2 kinases are phosphorylated/ activated by two immediate upstream MAP kinases (MEK1 and MEK2 (MEK1/2)) that are in turn phosphorylated/activated by several MAP kinases (i.e. MOS, C-Raf, and B-Raf). Activated ERK1/2 (pERK1/2) phosphorylates various downstream effectors involved in differentiation, proliferation, apoptosis, survival, cellular metabolism, and ion transport. The MAP kinase cascade may also be constitutively activated independent of external stimuli or ligands. This basal activity is the result of the balance between positive and negative factors regulating MAP kinases activity; that is, phosphatases, subcellular localization, expression of scaffold proteins, and activity of other kinases. In the kidney, the ERK1/2 pathway is involved in the hormonal regulation of different apical and basolateral channels or transporters expressed along the nephron for maintaining the extracellular fluid homeostasis. In the proximal tubule the ERK...

show abstract

Coexpression of alpha 1 with putative beta 3 subunits results in functional Na+/K+ pumps in Xenopus oocytes.

Cited by 57 publications

References 22 publications

Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes

Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes

The functional roles of disulfide bonds in the β‐subunit of (Na,K)ATPase as studied by site‐directed mutagenesis

ERK1/2 Controls Na,K-ATPase Activity and Transepithelial Sodium Transport in the Principal Cell of the Cortical Collecting Duct of the Mouse Kidney

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