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Unexpected Negative Role of the AT1R Adaptor Protein βarrestin1 in the ERK1/2 Activation of SHR‐Derived Primary Astrocytes
Author(s) -
Negussie Shmuel,
Lymperopoulos Anastasios,
Clark Michelle Alexa
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.719.6
Subject(s) - receptor , g protein coupled receptor , angiotensin ii , agonist , endocrinology , medicine , signal transduction , chemistry , g protein , astrocyte , messenger rna , arrestin , microbiology and biotechnology , biology , central nervous system , biochemistry , gene
Objective To investigate the role of βarrestin1 in angiotensin II (AngII) type 1 receptor (AT1R)‐mediated extracellular signal‐regulated kinase (ERK1/2) activation in spontaneously hypertensive rat (SHR)‐derived primary astrocytes. Background The βarrestins, consisting of two isoforms, βarrestin1 and ‐2, originally discovered as terminators of G protein signaling by G protein‐coupled receptors (GPCRs), are now known to also mediate their own signaling to ERK1/2 activation independently of G proteins. The AT1R is a GPCR that can also signal to ERK1/2 via βarrestins in various cell types. However, whether it can do so in the brain has not been investigated yet. Thus herein, we sought to examine the involvement of βarrestins in the AT1R‐mediated ERK1/2 activation in SHR‐derived primary astrocytes. Methods Primary cultures of rat astrocytes from brainstem were isolated from the brains of 2–3 days old pups obtained from pregnant SHR. 100 nM AngII and 10 μM SII (an AngII peptide analog which is βarrestin‐biased agonist) were used to study the AT1R mediated ERK1/2 activation. The results were compared to normotensive Wistar rats. Protein analysis was done using Western blotting and mRNA measurement was done using real time PCR. Results Our results indicate that βarrestin1 is the major arrestin protein in astrocytes from both SHR and normotensive rats. At the mRNA level however, both βarrestin1 and βarrestin2 display comparable expression. AngII activates ERK1/2 in SHR astrocytes much more robustly than in normotensive rat ones. On the other hand, SII strongly activates ERK1/2 in normotensive rat astrocytes and only minimally in SHR ones. Importantly, AngII also upregulates βarrestin1 protein in normotensive rat astrocytes, whereas in SHR astrocytes it has no significant effect. Finally, AngII downregulates both βarrestins at the mRNA level in both SHR and normotensive rat astrocytes. Conclusion The AngII‐AT1R‐induced ERK1/2 activation of SHR astrocytes, known to induce hypertension, appears to be almost exclusively G protein‐dependent, contrary to normotensive rat astrocytes. Since βarrestin1 protein is also upregulated by AngII in normotensive rat astrocytes and appears downregulated in SHR astrocytes, it is quite plausible that βarrestin1 may actually inhibit ERK1/2 activation in astrocytes. This might be a beneficial effect of βarrestin1 in preventing development of hypertension in the SHR condition. Support or Funding Information Funding for this research was provided through a Nova Southeastern University Health Professions Division Grant