Agonist

Summary

An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agonist, while an inverse agonist causes an action opposite to that of the agonist. Etymology From the Greek αγωνιστής (agōnistēs), contestant; champion; rival < αγων (agōn), contest, combat; exertion, struggle < αγω (agō), I lead, lead towards, conduct; drive Types of agonists Receptors can be activated by either endogenous agonists (such as hormones and neurotransmitters) or exogenous agonists (such as drugs), resulting in a biological response. A physiological agonist is a substance that creates the same bodily responses but does not bind to the same receptor.

An endogenous agonist for a particular receptor is a compound naturally produced by the body that binds to and activates that receptor. For example, the endoge

Official source

https://en.wikipedia.org/wiki/Agonist

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Structural basis of the activation of the CC chemokine receptor 5 by a chemokine agonist

Nicolas Calo, Polina Isaikina, Henning Paul-Julius Stahlberg

The human CC chemokine receptor 5 (CCR5) is a G protein-coupled receptor (GPCR) that plays a major role in inflammation and is involved in cancer, HIV, and COVID-19. Despite its importance as a drug target, the molecular activation mechanism of CCR5, i.e., how chemokine agonists transduce the activation signal through the receptor, is yet unknown. Here, we report the cryo-EM structure of wild-type CCR5 in an active conformation bound to the chemokine super-agonist [6P4]CCL5 and the heterotrimeric Gi protein. The structure provides the rationale for the sequence-activity relation of agonist and antagonist chemokines. The N terminus of agonist chemokines pushes onto specific structural motifs at the bottom of the orthosteric pocket that activate the canonical GPCR microswitch network. This activation mechanism differs substantially from other CC chemokine receptors that bind chemokines with shorter N termini in a shallow binding mode involving unique sequence signatures and a specialized activation mechanism.

AMER ASSOC ADVANCEMENT SCIENCE2021

Oligomerization of the alpha 1a- and alpha 1b-Adrenergic Receptor Subtypes: Potential Implications in Receptor Internalization

Susanna Cotecchia, Jean-Baptiste Perez, Laura Stanasila, Horst Vogel

We combined biophys., biochem., and pharmacol. approaches to investigate the ability of the a1a- and a1b-adrenergic receptor (AR) subtypes to form homo- and hetero-oligomers. Receptors tagged with different epitopes (hemagglutinin and Myc) or fluorescent proteins (cyan and green fluorescent proteins) were transiently expressed in HEK-293 cells either individually or in different combinations. Fluorescence resonance energy transfer measurements provided evidence that both the a1a- and a1b-AR can form homo-oligomers with similar transfer efficiency of .apprx.0.10. Hetero-oligomers could also be obsd. between the a1b- and the a1a-AR subtypes but not between the a1b-AR and the b2-AR, the NK1 tachykinin, or the CCR5 chemokine receptors. Oligomerization of the a1b-AR did not require the integrity of its C-tail, of two glycophorin motifs, or of the N-linked glycosylation sites at its N terminus. In contrast, helix I and, to a lesser extent, helix VII were found to play a role in the a1b-AR homo-oligomerization. Receptor oligomerization was not influenced by the agonist epinephrine or by the inverse agonist prazosin. A constitutively active (A293E) as well as a signaling-deficient (R143E) mutant displayed oligomerization features similar to those of the wild type a1b-AR. Confocal imaging revealed that oligomerization of the a1-AR subtypes correlated with their ability to co-internalize upon exposure to the agonist. The a1a-selective agonist oxymetazoline induced the co-internalization of the a1a- and a1b-AR, whereas the a1b-AR could not co-internalize with the NK1 tachykinin or CCR5 chemokine receptors. Oligomerization might therefore represent an addnl. mechanism regulating the physiol. responses mediated by the a1a- and a1b-AR subtypes. [on SciFinder (R)]

2003

Delivery of STING agonists for adjuvanting subunit vaccines

Bing Feng, Li Tang, Simon Bart M. Van Herck

Adjuvant is an essential component in subunit vaccines. Many agonists of pathogen recognition receptors have been developed as potent adjuvants to optimize the immunogenicity and efficacy of vaccines. Recently discovered cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway has attracted much attention as it is a key mediator for modulating immune responses. Vaccines adju-vanted with STING agonists are found to mediate a robust immune defense against infections and cancer. In this review, we first discuss the mechanisms of STING agonists in the context of vaccination. Next, we present recent progress in novel STING agonist discovery and the delivery strategies. We next highlight recent work in optimizing the efficacy while minimizing toxicity of STING agonist-assisted subunit vac-cines for protection against infectious diseases or treatment of cancer. Finally, we share our perspectives of current issues and future directions in further developing STING agonists for adjuvanting subunit vaccines. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

ELSEVIER2021