Professor Unidad Académica Multidisciplinaria Zona Media UASLP Rioverde S.L.P., San Luis Potosi, Mexico
Jesus Castillo-Hernandez (Unidad Académica Multidisciplinaria Zona Media UASLP)| Rafael Rubio (Facultad de Medicina de la UASLP)| Martha Maldonado-Cervantes (Unidad Académica Multidisciplinaria Zona Media UASLP)
We have shown that a 15,000 kDa polymer of Ang II (Ang II-POL) at maximal concentration upon a sustained action on the AT1R of rat coronary endothelial luminal membrane (CELM) produced sustained vasoconstriction and inotropic effects, and a lack of CELM AT1R internalization. In contrast, an equivalent concentration of the monomer Ang II (1 kDa) caused transient effects: desensitization, associated with the expected progressive internalization of CELM AT1R. It is accepted that AT1R Internalization into the cell, results from the CELM agonist-receptor complex sequestration into vesicles which depends on the internalization proteins: β-arrestin, clathrin and dynamin.
Objective: The purpose of this study was to study the effect of angII and AngII-POL on the recruitment of internalizing proteins: β arrestin and clathrin, in rat CELM. Hypothesis: The different rates of AT1R internalization induced by the monomer Ang II and the polymer Ang II-POL indicates that each agonist recruits in a different way the internalization proteins. Hypothesis test: In 2 groups hearts, time course inotropic Ang II or Ang II-POL effects were measured. In another groups, CELM proteins were isolated by the silica pellicle technique at various times from; control hearts, during stimulation with either Ang II or Ang II-POL, AT1R; β arrestina1/2 and clathrin quantified by Western blot.
Results: Ang II inotropic effects show desensitization, paralleled by CELM AT1R internalization, β-arrestin1/2 and Clathrin recruitment into CELM. In contrast Ang II-POL did not induce CELM AT1R internalization, it recruits considerable β-arrestin1/2 into CELM, without clathrin recruitment.
Conclusions: The activation mechanisms of AT1R by the monomer Ang II and the polymer Ang II-POL are distinct, because, in contrast to Ang II, the Ang II-POL effect, lacks of AT1R internalization, triggers an enhanced CELM β-arrestin1/2 recruitment with a much-reduced Clathrin recruitment. The likely resultant poor formation of clathrin-vesicles could explain the lack of AT1R internalization and suggest that clathrin density controls and limits the amount of β-arrestin1/2 incorporated. Clearly, Ang II-POL constitutes a powerful tool to understanding the mechanism of AT1R activation and internalization.