What question did this study set out to answer?

To determine whether the regulatory factor family members NHE-RF and E3KARP mediate cAMP-dependent inhibition and phosphorylation of NHE3, and whether phosphorylation of NHE-RF itself is required.

August 1, 1999Journal of Biological ChemistryOpen Access

cAMP-induced Phosphorylation and Inhibition of Na+/H+ Exchanger 3 (NHE3) Are Dependent on the Presence but Not the Phosphorylation of NHE Regulatory Factor

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Authors

MŽMirza ŽižakUniversity of Zagreb GLGeorg LamprechtUniversity of Rostock DSDeborah SteplockWest Virginia University

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Implication

Cellular study demonstrates that NHE-RF presence permits cAMP-mediated NHE3 phosphorylation and inhibition without requiring NHE-RF phosphorylation, indicating a scaffolding mechanism.

Key Points

To determine whether the regulatory factor family members NHE-RF and E3KARP mediate cAMP-dependent inhibition and phosphorylation of NHE3, and whether phosphorylation of NHE-RF itself is required.
Stably transfected PS120 fibroblasts with rabbit NHE3 alone, or co-expressed with wild-type rabbit NHE-RF, wild-type human E3KARP, or a triple-serine mutant NHE-RF (S287A, S289A, S290A).
Assayed Na+/H+ exchange activity and in vivo NHE3 phosphorylation following stimulation with 8-bromo-cAMP.
Performed co-immunoprecipitation experiments to evaluate physical associations between NHE3 and wild-type or mutant NHE-RF under basal and stimulated conditions.
8-Bromo-cAMP had no effect on Na+/H+ exchange in cells expressing NHE3 alone, but inhibited NHE3 activity by 39% in cells co-expressing NHE-RF.
cAMP stimulated phosphorylation across two chymotrypsin-generated phosphopeptides of NHE3 in the presence of NHE-RF or E3KARP, but failed to do so in their absence.
Mutant NHE-RF lacking basal phosphorylation still co-precipitated with NHE3 and facilitated 8-bromo-cAMP inhibition of NHE3 to the same extent as wild-type NHE-RF.

Cite This Study

Žižak et al. (1999) studied this question.

synapsesocial.com/papers/6a83372bb2f729353b1f2be9 https://doi.org/10.1074/jbc.274.35.24753

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Implication

Cellular study demonstrates that NHE-RF presence permits cAMP-mediated NHE3 phosphorylation and inhibition without requiring NHE-RF phosphorylation, indicating a scaffolding mechanism.

cAMP-induced Phosphorylation and Inhibition of Na+/H+ Exchanger 3 (NHE3) Are Dependent on the Presence but Not the Phosphorylation of NHE Regulatory Factor

Discussion

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Implication

Key Points

Cite This Study

cAMP-induced Phosphorylation and Inhibition of Na+/H+ Exchanger 3 (NHE3) Are Dependent on the Presence but Not the Phosphorylation of NHE Regulatory Factor

Discussion

Member takes

Implication

Key Points

Cite This Study

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