hormone response element

Examples of hormone response element in the following topics:

• Direct Gene Activation and the Second-Messenger System

  • Hormones can alter cell activity by binding with a receptor.
  • Upon binding to a hormone the receptor and hormone translocate into the nucleus, and bind to specific sequences of DNA known as hormone response elements (HREs).
  • Most hormone receptors are G protein-coupled receptors.
  • Hormone binding to the NR triggers translocation to the nucleus, where the NR binds to a specific sequence of DNA known as a hormone response element (HRE).
  • Distinguish between the hormone mechanisms of direct gene activation and the second-messenger system

• Intracellular Hormone Receptors

  • Lipid-derived (soluble) hormones such as steroid hormones diffuse across the lipid bilayer membranes of the endocrine cell.
  • In this way, the steroid hormone regulates specific cell processes .
  • Other lipid-soluble hormones that are not steroid hormones, such as vitamin D and thyroxine, have receptors located in the nucleus.
  • The hormone-receptor complex stimulates transcription of specific genes in the same way that steroid hormones do.
  • In the nucleus, the hormone-receptor complex binds to a DNA sequence called a hormone response element (HRE), which triggers gene transcription and translation.

• Lipid-Derived, Amino Acid-Derived, and Peptide Hormones

  • All hormones in the human body can be divided into lipid-derived, amino acid-derived, and peptide hormones.
  • The primary class of lipid hormones in humans is the steroid hormones.
  • They are then released in response to stimuli (e.g., as high blood glucose levels in the case of insulin).
  • The structures of peptide hormones (a) oxytocin, (b) growth hormone, and (c) follicle-stimulating hormone are shown.
  • (a) The hormone epinephrine, which triggers the fight-or-flight response, is derived from the amino acid tyrosine.

• Overview of Endocrine Glands

  • Two hormones—oxytocin and antidiuretic hormone (ADH)—are produced and released this way.
  • The anterior pituitary is involved in sending hormones that control all other hormones of the body.
  • Through hormonal secretions, they regulate many essential bodily functions including biochemical balances that influence athletic training and general stress response.
  • These are released into the small intestine to aid in reducing food particles to basic elements that can be absorbed by the intestine and used by the body.
  • These are responsible for releasing hormones in response to stress through the synthesis of corticosteroids such as cortisol, and catecholamines such as epinephrine (adrenaline) and norepinephrine.

• Humoral, Hormonal, and Neural Stimuli

  • A humoral stimulus refers to the control of hormone release in response to changes in extracellular fluids, such as the ion concentration in the blood.
  • Hormonal stimuli refers to the release of a hormone in response to another hormone.
  • A number of endocrine glands release hormones when stimulated by hormones released by other endocrine glands.
  • Recall that in a short-term stress response, the hormones epinephrine and norepinephrine are important for providing the bursts of energy required for the body to respond.
  • Here, neuronal signaling from the sympathetic nervous system directly stimulates the adrenal medulla to release the hormones epinephrine and norepinephrine in response to stress.

• How Hormones Work

  • Hormones mediate changes in target cells by binding to specific hormone receptors.
  • The number of receptors that respond to a hormone determines the cell's sensitivity to that hormone and the resulting cellular response.
  • In up-regulation, the number of receptors increases in response to rising hormone levels, making the cell more sensitive to the hormone, allowing for more cellular activity.
  • When the number of receptors decreases in response to rising hormone levels, called down-regulation, cellular activity is reduced.
  • The hormone binds to the receptor protein, resulting in the activation of a signal transduction mechanism that ultimately leads to cell type-specific responses.

• Pancreas

  • It contains both exocrine cells that excrete digestive enzymes and endocrine cells that release hormones.
  • Food particles are reduced to basic elements that can be absorbed by the intestine and used by the body.
  • The pancreatic islets contain two primary cell types: alpha cells, which produce the hormone glucagon, and beta cells, which produce the hormone insulin.
  • These hormones are responsible for the regulation of blood glucose levels.
  • Describe the hormones produced by the pancreas and the functions they regulate

• Hormone Receptors

  • Hormones activate a cellular response in the target cell by binding to a specific receptor in the target cell.
  • A hormone receptor is a molecule that binds to a specific hormone.
  • The hormone activity within a target cell is dependent on the effective concentration of hormone-receptor complexes that are formed.
  • Many hormones are composed of polypeptides—such as thyroid-stimulating hormones, follicle-stimulating hormones, luteinizing hormones, and insulin.
  • Ligand binding to the TR causes a dissociation of co-repressor and recruitment of co-activator proteins, which in turn recruit additional proteins (such as RNA polymerase) that are responsible for the transcription of downstream DNA into RNA, and eventually into protein that results in a change in cell function.

• Aging and the Endocrine System

  • Three hormone axes are affected by aging: growth hormone/insulin-like growth factor I, cortisol/dehydroepiandrosterone, and testoterone/estradiol.
  • The endocrine system consists of glands and organs that produce and release hormones that affect the body in different ways and help control functions including tissue homeostasis, growth and development, reproduction, response to stress, and metabolism.
  • In addition to lower circulating amounts of IGF-I, the responsiveness of bone to this protein has been shown to decrease in animal models.
  • DHEA is released from the adrenal cortex in response to adrenocorticotrophic hormone (ACTH).
  • Once it binds to the ER, a series of activation steps are initiated, resulting in the binding of the estrogen-ER complex to the estrogen responsive element (ERE).

• Plasma Membrane Hormone Receptors

  • Lipid-insoluble hormones bind to receptors on the outer surface of the plasma membrane, via plasma membrane hormone receptors.
  • The specific response of a cell to a lipid-insoluble hormone depends on the type of receptors that are present on the cell membrane and the substrate molecules present in the cell cytoplasm.
  • Cellular responses to hormone binding of a receptor include altering membrane permeability and metabolic pathways, stimulating synthesis of proteins and enzymes, and activating hormone release.
  • Hormone binding to receptor activates a G protein, which in turn activates adenylyl cyclase, converting ATP to cAMP. cAMP is a second messenger that mediates a cell-specific response.
  • Describe the events that occur when a hormone binds to a plasma hormone receptor