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Spinophilin Is Indispensable for the α2B Adrenergic Receptor-Elicited Hypertensive Response.

Che P, Chen Y, Lu R, Peng N, Gannon M, Wyss JM, Jiao K, Wang Q - PLoS ONE (2015)

Bottom Line: In arrestin 3 deficient mice, where the receptor has a stronger binding to spinophilin, the same hypertensive response is enhanced.These data suggest that interaction with spinophilin is indispensable for the α2BAR to elicit the hypertensive response.Thus, spinophilin may represent a useful therapeutic target for treatment of hypertension.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, 1918 University Boulevard, Birmingham, AL 35294, United States of America.

ABSTRACT
The α2 adrenergic receptor (AR) subtypes are important for blood pressure control. When activated, the α2A subtype elicits a hypotensive response whereas the α2B subtype mediates a hypertensive effect that counteracts the hypotensive response by the α2A subtype. We have previously shown that spinophilin attenuates the α2AAR-dependent hypotensive response; in spinophilin mice, this response is highly potentiated. In this study, we demonstrate that spinophilin impedes arrestin-dependent phosphorylation and desensitization of the α2BAR subtype by competing against arrestin binding to this receptor subtype. The Del301-303 α2BAR, a human variation that shows impaired phosphorylation and desensitization and is linked to hypertension in certain populations, exhibits preferential interaction with spinophilin over arrestin. Furthermore, Del301-303 α2BAR-induced ERK signaling is quickly desensitized in cells without spinophilin expression, showing a profile similar to that induced by the wild type receptor in these cells. Together, these data suggest a critical role of spinophilin in sustaining α2BAR signaling. Consistent with this notion, our in vivo study reveals that the α2BAR-elicited hypertensive response is diminished in spinophilin deficient mice. In arrestin 3 deficient mice, where the receptor has a stronger binding to spinophilin, the same hypertensive response is enhanced. These data suggest that interaction with spinophilin is indispensable for the α2BAR to elicit the hypertensive response. This is opposite of the negative role of spinophilin in regulating α2AAR-mediated hypotensive response, suggesting that spinophilin regulation of these closely related receptor subtypes can result in distinct functional outcomes in vivo. Thus, spinophilin may represent a useful therapeutic target for treatment of hypertension.

No MeSH data available.


Related in: MedlinePlus

Spinophilin is required for maintaining the sustained ERK1/2 activation induced by the Del301-303 α2BAR in MEFs.(A) Sp+/+ MEFs expressing the WT or Del301-303 α2BAR were stimulated with 1μM clonidine for indicated time points. Representative blots show phospho- and total-ERK1/2. (B) Quantitation of ERK1/2 activation in Sp+/+ MEFs. The relative ERK1/2 activation at each time point was expressed as a ratio to the peak level of ERK1/2 activation in the same experiment, which was arbitrarily defined as 1.0. n = 7 for the WT α2B group and n = 6 for the Del301-303 α2B group. *, p<0.05; ***, p<0.001, WT α2Bvs. Del301-303 α2B. (C) Sp-/- MEFs expressing the WT or Del301-303 α2BAR were stimulated with 1μM clonidine for indicated time points. Representative blots show phospho- and total-ERK1/2. (D) Quantitation of ERK1/2 activation in Sp-/- MEFs. n = 4 for the WT α2B group and n = 3 for the Del301-303 α2B group.
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pone.0135030.g007: Spinophilin is required for maintaining the sustained ERK1/2 activation induced by the Del301-303 α2BAR in MEFs.(A) Sp+/+ MEFs expressing the WT or Del301-303 α2BAR were stimulated with 1μM clonidine for indicated time points. Representative blots show phospho- and total-ERK1/2. (B) Quantitation of ERK1/2 activation in Sp+/+ MEFs. The relative ERK1/2 activation at each time point was expressed as a ratio to the peak level of ERK1/2 activation in the same experiment, which was arbitrarily defined as 1.0. n = 7 for the WT α2B group and n = 6 for the Del301-303 α2B group. *, p<0.05; ***, p<0.001, WT α2Bvs. Del301-303 α2B. (C) Sp-/- MEFs expressing the WT or Del301-303 α2BAR were stimulated with 1μM clonidine for indicated time points. Representative blots show phospho- and total-ERK1/2. (D) Quantitation of ERK1/2 activation in Sp-/- MEFs. n = 4 for the WT α2B group and n = 3 for the Del301-303 α2B group.

Mentions: The above data suggest that the diminished affinity of the Del301-303 α2BAR for β-arrestin binding likely underlies impaired desensitization of signaling elicited by this receptor variant. Since the Del301-303 α2BAR showed increased interaction with spinophilin, we further sought to address whether spinophilin binding to this receptor plays a role in sustaining its prolonged signaling. We therefore examined the kinetics of ERK1/2 signaling elicited by the WT or Del301-303 α2BAR in Sp-/- and the corresponding Sp+/+ MEFs. Consistent with the reduced desensitization of the Del301-303 α2BAR signaling reported previously [27], ERK1/2 activation elicited by the Del301-303 α2BAR was prolonged when compared to that elicited by the WT α2BAR in Sp+/+ MEFs (Fig 7A and 7B). Strikingly, in Sp-/- MEF, we failed to observe any difference in ERK1/2 activation kinetics induced by the Del301-303 versus the WT α2BAR (Fig 7C and 7D). In both cases, ERK1/2 signaling was quickly desensitized (Fig 7C and 7D). These data suggest that spinophilin is required for sustaining the prolonged ERK1/2 signaling elicited by the Del301-303 α2BAR.


Spinophilin Is Indispensable for the α2B Adrenergic Receptor-Elicited Hypertensive Response.

Che P, Chen Y, Lu R, Peng N, Gannon M, Wyss JM, Jiao K, Wang Q - PLoS ONE (2015)

Spinophilin is required for maintaining the sustained ERK1/2 activation induced by the Del301-303 α2BAR in MEFs.(A) Sp+/+ MEFs expressing the WT or Del301-303 α2BAR were stimulated with 1μM clonidine for indicated time points. Representative blots show phospho- and total-ERK1/2. (B) Quantitation of ERK1/2 activation in Sp+/+ MEFs. The relative ERK1/2 activation at each time point was expressed as a ratio to the peak level of ERK1/2 activation in the same experiment, which was arbitrarily defined as 1.0. n = 7 for the WT α2B group and n = 6 for the Del301-303 α2B group. *, p<0.05; ***, p<0.001, WT α2Bvs. Del301-303 α2B. (C) Sp-/- MEFs expressing the WT or Del301-303 α2BAR were stimulated with 1μM clonidine for indicated time points. Representative blots show phospho- and total-ERK1/2. (D) Quantitation of ERK1/2 activation in Sp-/- MEFs. n = 4 for the WT α2B group and n = 3 for the Del301-303 α2B group.
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pone.0135030.g007: Spinophilin is required for maintaining the sustained ERK1/2 activation induced by the Del301-303 α2BAR in MEFs.(A) Sp+/+ MEFs expressing the WT or Del301-303 α2BAR were stimulated with 1μM clonidine for indicated time points. Representative blots show phospho- and total-ERK1/2. (B) Quantitation of ERK1/2 activation in Sp+/+ MEFs. The relative ERK1/2 activation at each time point was expressed as a ratio to the peak level of ERK1/2 activation in the same experiment, which was arbitrarily defined as 1.0. n = 7 for the WT α2B group and n = 6 for the Del301-303 α2B group. *, p<0.05; ***, p<0.001, WT α2Bvs. Del301-303 α2B. (C) Sp-/- MEFs expressing the WT or Del301-303 α2BAR were stimulated with 1μM clonidine for indicated time points. Representative blots show phospho- and total-ERK1/2. (D) Quantitation of ERK1/2 activation in Sp-/- MEFs. n = 4 for the WT α2B group and n = 3 for the Del301-303 α2B group.
Mentions: The above data suggest that the diminished affinity of the Del301-303 α2BAR for β-arrestin binding likely underlies impaired desensitization of signaling elicited by this receptor variant. Since the Del301-303 α2BAR showed increased interaction with spinophilin, we further sought to address whether spinophilin binding to this receptor plays a role in sustaining its prolonged signaling. We therefore examined the kinetics of ERK1/2 signaling elicited by the WT or Del301-303 α2BAR in Sp-/- and the corresponding Sp+/+ MEFs. Consistent with the reduced desensitization of the Del301-303 α2BAR signaling reported previously [27], ERK1/2 activation elicited by the Del301-303 α2BAR was prolonged when compared to that elicited by the WT α2BAR in Sp+/+ MEFs (Fig 7A and 7B). Strikingly, in Sp-/- MEF, we failed to observe any difference in ERK1/2 activation kinetics induced by the Del301-303 versus the WT α2BAR (Fig 7C and 7D). In both cases, ERK1/2 signaling was quickly desensitized (Fig 7C and 7D). These data suggest that spinophilin is required for sustaining the prolonged ERK1/2 signaling elicited by the Del301-303 α2BAR.

Bottom Line: In arrestin 3 deficient mice, where the receptor has a stronger binding to spinophilin, the same hypertensive response is enhanced.These data suggest that interaction with spinophilin is indispensable for the α2BAR to elicit the hypertensive response.Thus, spinophilin may represent a useful therapeutic target for treatment of hypertension.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, 1918 University Boulevard, Birmingham, AL 35294, United States of America.

ABSTRACT
The α2 adrenergic receptor (AR) subtypes are important for blood pressure control. When activated, the α2A subtype elicits a hypotensive response whereas the α2B subtype mediates a hypertensive effect that counteracts the hypotensive response by the α2A subtype. We have previously shown that spinophilin attenuates the α2AAR-dependent hypotensive response; in spinophilin mice, this response is highly potentiated. In this study, we demonstrate that spinophilin impedes arrestin-dependent phosphorylation and desensitization of the α2BAR subtype by competing against arrestin binding to this receptor subtype. The Del301-303 α2BAR, a human variation that shows impaired phosphorylation and desensitization and is linked to hypertension in certain populations, exhibits preferential interaction with spinophilin over arrestin. Furthermore, Del301-303 α2BAR-induced ERK signaling is quickly desensitized in cells without spinophilin expression, showing a profile similar to that induced by the wild type receptor in these cells. Together, these data suggest a critical role of spinophilin in sustaining α2BAR signaling. Consistent with this notion, our in vivo study reveals that the α2BAR-elicited hypertensive response is diminished in spinophilin deficient mice. In arrestin 3 deficient mice, where the receptor has a stronger binding to spinophilin, the same hypertensive response is enhanced. These data suggest that interaction with spinophilin is indispensable for the α2BAR to elicit the hypertensive response. This is opposite of the negative role of spinophilin in regulating α2AAR-mediated hypotensive response, suggesting that spinophilin regulation of these closely related receptor subtypes can result in distinct functional outcomes in vivo. Thus, spinophilin may represent a useful therapeutic target for treatment of hypertension.

No MeSH data available.


Related in: MedlinePlus