Effects of agonists and phorbol esters on α<inf>1A</inf>-adrenergic receptor-Rab protein interactions

de-los-Santos-Cocotle, G., Martínez-Morales, J. C., Romero-Ávila, M. T., Reyes-Cruz, G., & García-Sáinz, J. A. (2020). Effects of agonists and phorbol esters on ?1A-adrenergic receptor-Rab protein interactions. European Journal of Pharmacology, 885, 173423. doi:10.1016/j.ejphar.2020.173423

ABSTRACT

In a cell line, stably expressing α-adrenoceptors fused to the mCherry red fluorescent protein, noradrenaline, methoxamine, and oxymetazoline induced concentration-dependent increases in intracellular calcium. All of these agents increase α-adrenoceptor phosphorylation and internalization. Transient co-expression of these receptors with Rab proteins tagged with the enhanced Green Fluorescent Protein was employed to estimate α-adrenoceptor-Rab interaction using Förster Resonance Energy Transfer. Noradrenaline and methoxamine increased α-adrenoceptor interaction with Rab5 and Rab7 but did not modify it with Rab9. Oxymetazoline induced adrenoceptor interaction with Rab5 and Rab9 and only an insignificant increase in Rab7 signal. Phorbol myristate acetate increased α-adrenoceptor interaction with Rab5 and Rab9 but did not modify it with Rab7. The agonists and the active phorbol ester, all of which induce receptor phosphorylation and internalization, favor receptor interaction with Rab5, i.e., association with early endosomes. Cell stimulation with phorbol myristate acetate induced the α-adrenoceptors to interact with the late endosomal marker, Rab9, suggesting that the receptors are directed to slow recycling endosomes once they have transited to the Trans-Golgi network to be retrieved to the plasma membrane. The agonists noradrenaline and methoxamine likely induce a faster recycling and might direct some of the adrenoceptors toward degradation and/or very slow recycling to the plasma membrane. Oxymetazoline produced a mixed pattern of interaction with the Rab proteins. These data indicate that α-adrenoceptor agonists can trigger different vesicular traffic and receptor fates within the cells.



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