Luminal ANG II is internalized as a complex with AT^sub 1^R/AT^sub 2^R heterodimers to target endoplasmic reticulum in LLC-PK^sub 1^ cells

ANG II has many biological effects in renal physiology, particularly in Ca2+ handling in the regulation of fluid and solute reabsorption. It involves the systemic endocrine renin-angiotensin system (RAS), but tissue and intracrine ANG II are also known. We have shown that ANG II induces heterodimeri...

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Bibliographic Details
Published in:American journal of physiology. Renal physiology 2017-08, Vol.313 (2), p.F440
Main Authors: Ferrão, Fernanda M, Cardoso, Luiza HD, Drummond, Heather A, Li, Xiao C, Zhuo, Jia L, Gomes, Dayene S, Lara, Lucienne S, Vieyra, Adalberto, Lowe, Jennifer
Format: Article
Language:English
Subjects:
Angiotensin
Angiotensin II
Arrestin
Ca2+-transporting ATPase
Cells
Clathrin
Dephosphorylation
Endocytosis
Endoplasmic reticulum
Internalization
Intracellular
Kidneys
Localization
Phosphorylation
Protein kinase C
Reabsorption
Renin
Tissues
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Summary:ANG II has many biological effects in renal physiology, particularly in Ca2+ handling in the regulation of fluid and solute reabsorption. It involves the systemic endocrine renin-angiotensin system (RAS), but tissue and intracrine ANG II are also known. We have shown that ANG II induces heterodimerization of its AT1 and AT2 receptors (AT1R and AT2R) to stimulate sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) activity. Thus, we investigated whether ANG II-AT1R/AT2R complex is formed and internalized, and also examined the intracellular localization of this complex to determine how its effect might be exerted on renal intracrine RAS. Living cell imaging of LLC-PK1 cells, quantification of extracellular ANG II, and use of the receptor antagonists, losartan and PD123319, showed that ANG II is internalized with AT1R/AT2R heterodimers as a complex in a microtubule-dependent and clathrin-independent manner, since colchicines -- but not Pitstop2 -- blocked this process. This result was confirmed by an increase of β-arrestin phosphorylation after ANG II treatment, clathrin-mediated endocytosis being dependent on dephosphorylation of β-arrestin. Internalized ANG II colocalized with an endoplasmic reticulum (ER) marker and increased levels of AT1R, AT2R, and PKCα in ER-enriched membrane fractions. This novel evidence suggests the internalization of an ANG II-AT1/AT2 complex to target ER, where it might trigger intracellular Ca2+ responses.
ISSN:1931-857X
1522-1466