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Epithelial sodium channel abundance is decreased by an unfolded protein response induced by hyperosmolality.

Crambert G, Ernandez T, Lamouroux C, Roth I, Dizin E, Martin PY, Féraille E, Hasler U - Physiol Rep (2014)

Bottom Line: Hyperosmotic stress profoundly challenges cellular homeostasis and induces endoplasmic reticulum (ER) stress.Both hyperosmolality and chemical induction of ER stress decreased ENaC expression in vitro.ENaC depletion by either stimulus was abolished by transcriptional inhibition and by the chemical chaperone 4-phenylbutyric acid and was partly abrogated by either PERK or ATF6 silencing.

View Article: PubMed Central - PubMed

Affiliation: UPMC/INSERM/Paris Descartes U1138 CNRS ERL 8228, Equipe 3 Métabolisme et Physiologie Rénale, Centre de Recherche des Cordeliers, Paris, France.

No MeSH data available.


Related in: MedlinePlus

PERK, IREα and ATF6 differently influence abundance of each ENaC subunit. (A and B) mRNA abundance of ATF3 (A) and ENaC (B) in cells challenged or not with NaCl (500 mOsmol/kg), Tg (Tg, 1 μmol/L) or Tun (Tun, 3 μmol/L) in the presence or absence (Ctl) of 4‐phenylbutyric acid (PBA, 20 mmol/L) for 6 h. Data is represented as fold difference over non‐stimulated cells and is expressed as the mean ± SEM of four independent experiments. (C–H) Cells transfected with scramble siRNA or siRNA against PERK (siPERK, C and D), IRE1 (siIRE1, E and F) or ATF6 (siATF6, G and H) were challenged or not (Ctl) with NaCl, Tg or Tun for 6 h. Target gene and ATF3 (C, E and G) and ENaC (D, F and H) mRNA abundance was analyzed by Q‐PCR. Data is represented as fold difference over non‐stimulated cells transfected with scramble siRNA and is expressed as the mean ± SEM of four independent experiments.
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fig06: PERK, IREα and ATF6 differently influence abundance of each ENaC subunit. (A and B) mRNA abundance of ATF3 (A) and ENaC (B) in cells challenged or not with NaCl (500 mOsmol/kg), Tg (Tg, 1 μmol/L) or Tun (Tun, 3 μmol/L) in the presence or absence (Ctl) of 4‐phenylbutyric acid (PBA, 20 mmol/L) for 6 h. Data is represented as fold difference over non‐stimulated cells and is expressed as the mean ± SEM of four independent experiments. (C–H) Cells transfected with scramble siRNA or siRNA against PERK (siPERK, C and D), IRE1 (siIRE1, E and F) or ATF6 (siATF6, G and H) were challenged or not (Ctl) with NaCl, Tg or Tun for 6 h. Target gene and ATF3 (C, E and G) and ENaC (D, F and H) mRNA abundance was analyzed by Q‐PCR. Data is represented as fold difference over non‐stimulated cells transfected with scramble siRNA and is expressed as the mean ± SEM of four independent experiments.

Mentions: We examined the effects of modulated UPR activity on ENaC abundance. Chemical attenuation of ER stress by 4‐phenylbutyric acid (PBA) abolished induction of ER‐stress responsive genes by NaCl, Tg and Tun, as illustrated by blunted ATF3 induction (Fig. 6A). PBA also abolished the effects of NaCl, Tg and Tun on all three ENaC subunits (Fig. 6B). We next investigated how each UPR arm affects ENaC abundance by transfecting cells with siRNA against PERK, IRE1α or ATF6. Globally, each siRNA reduced ATF3 induction by NaCl, Tg or Tun but to a significantly smaller extent than PBA (Fig. 6C, E and G). This may be expected since decreased activity of any one UPR mediator is likely to be at least partly compensated by other UPR arms (Ron and Walter 2007). Because simultaneous downregulation of all three UPR mediators blunted cell proliferation, we were unable to analyze their combined effects. Attenuated PERK expression partly blunted the effect of NaCl, Tg and Tun on ENaCα, but not ENaCβ or ENaCγ (Fig. 6D). Similar results were obtained when IRE1α expression was attenuated, but only in cells challenged with Tg or Tun (Fig. 6F), corroborating our observation that IRE1α is not significantly activated by NaCl (Fig. 5B). XBP‐1 silencing by siRNA did not significantly affect decreased abundance of any ENaC subunit by either NaCl, Tg or Tun (not shown). Attenuated ATF6 expression had no effect on ENaCα abundance but increased basal levels of both ENaCβ and ENaCγ mRNA and partly blunted their decreased abundance by NaCl, Tg and Tun (Fig. 6H).


Epithelial sodium channel abundance is decreased by an unfolded protein response induced by hyperosmolality.

Crambert G, Ernandez T, Lamouroux C, Roth I, Dizin E, Martin PY, Féraille E, Hasler U - Physiol Rep (2014)

PERK, IREα and ATF6 differently influence abundance of each ENaC subunit. (A and B) mRNA abundance of ATF3 (A) and ENaC (B) in cells challenged or not with NaCl (500 mOsmol/kg), Tg (Tg, 1 μmol/L) or Tun (Tun, 3 μmol/L) in the presence or absence (Ctl) of 4‐phenylbutyric acid (PBA, 20 mmol/L) for 6 h. Data is represented as fold difference over non‐stimulated cells and is expressed as the mean ± SEM of four independent experiments. (C–H) Cells transfected with scramble siRNA or siRNA against PERK (siPERK, C and D), IRE1 (siIRE1, E and F) or ATF6 (siATF6, G and H) were challenged or not (Ctl) with NaCl, Tg or Tun for 6 h. Target gene and ATF3 (C, E and G) and ENaC (D, F and H) mRNA abundance was analyzed by Q‐PCR. Data is represented as fold difference over non‐stimulated cells transfected with scramble siRNA and is expressed as the mean ± SEM of four independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4255800&req=5

fig06: PERK, IREα and ATF6 differently influence abundance of each ENaC subunit. (A and B) mRNA abundance of ATF3 (A) and ENaC (B) in cells challenged or not with NaCl (500 mOsmol/kg), Tg (Tg, 1 μmol/L) or Tun (Tun, 3 μmol/L) in the presence or absence (Ctl) of 4‐phenylbutyric acid (PBA, 20 mmol/L) for 6 h. Data is represented as fold difference over non‐stimulated cells and is expressed as the mean ± SEM of four independent experiments. (C–H) Cells transfected with scramble siRNA or siRNA against PERK (siPERK, C and D), IRE1 (siIRE1, E and F) or ATF6 (siATF6, G and H) were challenged or not (Ctl) with NaCl, Tg or Tun for 6 h. Target gene and ATF3 (C, E and G) and ENaC (D, F and H) mRNA abundance was analyzed by Q‐PCR. Data is represented as fold difference over non‐stimulated cells transfected with scramble siRNA and is expressed as the mean ± SEM of four independent experiments.
Mentions: We examined the effects of modulated UPR activity on ENaC abundance. Chemical attenuation of ER stress by 4‐phenylbutyric acid (PBA) abolished induction of ER‐stress responsive genes by NaCl, Tg and Tun, as illustrated by blunted ATF3 induction (Fig. 6A). PBA also abolished the effects of NaCl, Tg and Tun on all three ENaC subunits (Fig. 6B). We next investigated how each UPR arm affects ENaC abundance by transfecting cells with siRNA against PERK, IRE1α or ATF6. Globally, each siRNA reduced ATF3 induction by NaCl, Tg or Tun but to a significantly smaller extent than PBA (Fig. 6C, E and G). This may be expected since decreased activity of any one UPR mediator is likely to be at least partly compensated by other UPR arms (Ron and Walter 2007). Because simultaneous downregulation of all three UPR mediators blunted cell proliferation, we were unable to analyze their combined effects. Attenuated PERK expression partly blunted the effect of NaCl, Tg and Tun on ENaCα, but not ENaCβ or ENaCγ (Fig. 6D). Similar results were obtained when IRE1α expression was attenuated, but only in cells challenged with Tg or Tun (Fig. 6F), corroborating our observation that IRE1α is not significantly activated by NaCl (Fig. 5B). XBP‐1 silencing by siRNA did not significantly affect decreased abundance of any ENaC subunit by either NaCl, Tg or Tun (not shown). Attenuated ATF6 expression had no effect on ENaCα abundance but increased basal levels of both ENaCβ and ENaCγ mRNA and partly blunted their decreased abundance by NaCl, Tg and Tun (Fig. 6H).

Bottom Line: Hyperosmotic stress profoundly challenges cellular homeostasis and induces endoplasmic reticulum (ER) stress.Both hyperosmolality and chemical induction of ER stress decreased ENaC expression in vitro.ENaC depletion by either stimulus was abolished by transcriptional inhibition and by the chemical chaperone 4-phenylbutyric acid and was partly abrogated by either PERK or ATF6 silencing.

View Article: PubMed Central - PubMed

Affiliation: UPMC/INSERM/Paris Descartes U1138 CNRS ERL 8228, Equipe 3 Métabolisme et Physiologie Rénale, Centre de Recherche des Cordeliers, Paris, France.

No MeSH data available.


Related in: MedlinePlus