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Hormone receptor: Chosen article.

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A hormone receptor is a receptor molecule that binds to a specific hormone. Hormone receptors are a wide family of proteins made up of receptors for thyroid and steroid hormones, retinoids and Vitamin D, and a variety of other receptors for various ligands, such as fatty acids and prostaglandins. There are two main classes of hormone receptors. Receptors for peptide hormones tend to be cell surface receptors built into the plasma membrane of cells and are thus referred to as trans membrane receptors. An example of this is insulin. Receptors for steroid hormones are usually found within the cytoplasm and are referred to as intracellular or nuclear receptors, such as testosterone. Upon hormone binding, the receptor can induce multiple signaling pathways which can lead to a wide variety of changes in the behavior of the target cells.

General Ligand Binding

Signal molecule binds to its hormone receptor, inducing a conformational change in the receptor to begin a signaling cascade that will induce a cellular response.

Hormone receptor proteins bind to a hormone as a result of an accumulation of weak interactions. Because of the relatively large size of enzymes and receptors, the great amount of surface area provides the basis for these weak interactions to occur. This binding is highly specific because of the complementarity of these interactions between polar, non-polar, charged, neutral, hydrophilic, or hydrophobic residues. Upon binding, the receptor often undergoes a conformational change to induce multiple signaling pathways. Because of these highly specific and high affinity interactions between hormones and their receptors, very low concentrations of hormone are needed to produce significant cellular response. Receptors can have various different structures depending on the function of the hormone and the structure of its ligand.

Functions

Transmission of Signal [edit | edit source]

Intracellular (Nuclear Receptors)

Intracellular and nuclear receptors are the most direct way for the cell to respond to immediate changes within itself. Intracellular receptors are activated by hydrophobic ligands which pass through the cellular membrane. Nuclear receptors are a special class of intracellular receptor which specifically aid the needs of the cell to express certain genes.

Trans-Membrane Receptors

The extracellular environment is able to induce changes within the cell. Hormones, or other extracellular signals are able to induce changes within the cell by binding to membrane-bound receptors. This interaction allows the hormone receptor to produce second messengers within the cell to aid response. Second messengers may also be sent to interact with intracellular receptors.

Aiding Gene Expression [edit | edit source]

Hormone receptors can behave as transcription factors by interacting directly with DNA or by cross-talking with signaling pathways. This process is mediated through co-regulators. In the absence of ligand, receptor molecules bind corepressors in order to repress gene expression, compacting chromatin through histone deacetylatase. When ligand is present, nuclear receptors undergo a conformational change to recruit various coactivators. These molecules work to remodel chromatin. Hormone receptors have highly specific motifs which are able to interact with coregulator complexes. This is the mechanism through which receptors can induce regulation of gene expression depending on both the extracellular environment and the immediate cellular composition. Steroid hormones and their regulation by receptors are the most potent molecule interactions in aiding gene expression.

Classification [edit | edit source]

Receptors for water-soluble hormones[edit | edit source]

Water-soluble hormones include glycoproteins, catecholamines, and peptide hormones composed of polypeptides, e.g. thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone and insulin. These molecules are not lipid-soluble and therefore cannot diffuse through cell membranes. Consequently, receptors for peptide hormones are located on the plasma membrane.

The main two types of transmembrane receptor hormone receptor are the G-protein-coupled receptors and the enzyme-linked receptors. These receptors generally function via intracellular second messengers, including cyclic AMP (cAMP), cyclic GMP (cGMP), inositol 1,4,5-trisphosphate (IP3) and the calcium (Ca2+)-calmodulinsystem.

Receptors for lipid-soluble hormones[edit | edit source]

Steroid hormone receptors and related receptors are generally soluble proteins that function through gene activation. Their response elements are DNA sequences (promoters) that are bound by the complex of the steroid bound to its receptor. The receptors themselves are zinc-finger proteins.[1] These receptors include those forglucocorticoids (glucocorticoid receptors), estrogens (estrogen receptors), androgens (androgen receptors), thyroid hormone (T3) (thyroid hormone receptors), calcitriol(the active form of vitamin D) (calcitriol receptors), and the retinoids (vitamin A) (retinoid receptors). Receptor-protein interactions induce the uptake and destruction of their respective hormones in order to regulate their concentration in the body. [2]

List of hormone receptors[edit | edit source]

This list is incomplete; you can help by expanding it.

For some of these classes, in any given species (such as, for example, humans), there is a single molecule encoded by a single gene; in other cases, there are several molecules in the class.

• Androgen receptors
• Calcitriol receptors
• Corticotropin-releasing hormone receptor 1
• Corticotropin releasing hormone receptor 2
• Estrogen receptors
• Follicle-stimulating hormone receptors
• Glucagon receptors
• Gonadotropin receptors
• Gonadotropin-releasing hormone receptors
• Growth hormone receptors
• Luteinizing hormone receptors
• Progesterone receptors
• Retinoid receptors
• Somatostatin receptors
• Thyroid hormone receptors
• Thyrotropin receptor

Hormone Receptors

Hormone receptors are a wide family made up of receptors for thyroid and steroid hormones, retinoids and Vitamin D, and a variety of orphan receptors of various ligands, such as fatty acids and prostaglandins. Hormone receptor proteins bind to a hormone as a result of an accumulation of weak interactions. Because of the relatively large size of enzymes and receptors, the great amount of surface area provides the basis for these weak interactions to occur. This binding is highly specific because of the complementarity of these interactions between polar, non-polar, charged, neutral, hydrophilic, or hydrophobic residues. Hormone receptors can induce a wide variety of changes within a cell.

Transmission of Signal

Cells have the ability to respond to their surrounding environment through the signaling of hormones. These hormones or other extracellular signals interact with the hormone receptors on the cell surface to often produce second messengers within the cell. These second messengers then induce changes within the cell.

Aiding Gene Expression

Hormone receptors can behave as transcription factors by interacting with dimers or other signaling pathways. This process is mediated through co-regulators, where receptor molecules bind corepressors in order to repress gene expression when ligand is not present, compacting chromatin through histone deacetylatase. When ligand is present, hormone receptors undergo a conformational change which induces the recruitment of various coactivators. These molecules work to remodel chromatin. The interactions which hormone receptors, which can form highly specific motifs, can have with coregulator complexes is a part of the mechanism through which receptors can induce regulation of gene expression through affecting transcription.

Hi, Wikipedia Community! I am looking to edit this page and have a few ideas on things that I would like to add.

I am planning on extending the introduction/definition of hormone receptors. Firstly, I want to assert how cells respond to their environment based on hormones and chemical signaling that occurs between hormones and their receptors, and how the extracellular environment induces changes on the inside on the cell. Also, I am going to touch on how hormone receptors can aid gene expression. I want to touch on (whether in the initial section or subsequent segments, depending on how I think the organization will be best) the different ways hormone receptors can act (potent signals, extracellular signals, intracellular signals are the most likely things I will touch on).

I am going to add a section on binding to hormone receptors, which will include how the binding of a hormone to its receptor occurs as a result of weak interactions and how the structure of receptors allows these interactions to occur. I feel that this is important in showing how these receptors function so well and allow the basis for interaction in order to contribute to cell signaling.

Additionally, I would like to elaborate on both the water-soluble and lipid-soluble sections and elaborate on the purposes and functions of them because right now those sections are limited to how they work, rather than what they contribute to and do.

Lastly, the page contains a list of examples of hormone receptors. While I think keeping this as a list is best because those pages contain the information that I would likely add, I think separating these lists into different characterizations of hormone receptors would provide a stronger organization and lead to a better understanding if somebody is coming to the page to look for something specific.

Hope this sounds good! Any feedback would be appreciated.

References:

1. Nelson, David L., Michael M. Cox, and Albert L. Lehninger. Lehninger Principles of Biochemistry. New York: Worth, 2000. Print. 2. Aranda, A. "Nuclear Hormone Receptors and Gene Expression." National Library of Medicine. N.p., n.d. Web. 3. Moehren, U., M. Eckey, and A. Baniahmad. "Result Filters." National Center for Biotechnology Information. U.S. National Library of Medicine, 2004. Web. 05 May 2016. — Preceding unsigned comment added by Alexkeir (talk • contribs) 04:43, 5 May 2016 (UTC)

Enzyme catalysis page: Adding a section on Metal ion catalysis, which lacks a section on this page for homework due Week 5.

Metal Ion Catalysis

The presence of a metal ion in the active site participates in catalysis by coordinating charge stabilization and shielding. Because of a metal's positive charge, only negative charges can be stabilized through metal ions. Metal ions can also act to ionize water by acting as a Lewis acid. Metal ions may also be agents of oxidation and reduction.

. Sub-Heading 1

Where more information goes.

Block quote that is important to idea and remains separate from the rest of the text.

Wiki Education Foundation-supported course assignment

This article is or was the subject of a Wiki Education Foundation-supported course assignment. Further details are available on the course page. Student editor(s): Alexkeir.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 14:35, 18 January 2022 (UTC)