nuclear receptor

Examples of nuclear receptor in the following topics:

• Direct Gene Activation and the Second-Messenger System

  • Nuclear receptors function as transcription factors because they can bind to DNA and regulate gene expression.
  • Receptors that can directly influence gene expression are termed nuclear receptors.
  • Type I nuclear receptors are located in the cytosol.
  • In the absence of ligand, type II nuclear receptors often form a complex with co-repressor proteins.
  • Hormone binding to the nuclear receptor results in dissociation of the co-repressor and the recruitment of co-activator proteins.

• Intracellular Hormone Receptors

  • They then adhere to intracellular receptors residing in the cytoplasm or in the nucleus.
  • The hormones diffuse across both the plasma membrane and the nuclear envelope, then bind to receptors in the nucleus.
  • An intracellular nuclear receptor (NR) is located in the cytoplasm bound to a heat shock protein (HSP).
  • Upon hormone binding, the receptor dissociates from the heat shock protein and translocates to the nucleus.
  • Describe how hormones alter cellular activity by binding to intracellular receptors

• Mechanisms of Hormone Action

  • Hormones activate target cells by diffusing through the plasma membrane of the target cells (lipid-soluble hormones) to bind a receptor protein within the cytoplasm of the cell, or by binding a specific receptor protein in the cell membrane of the target cell (water-soluble proteins).
  • Recognition of the hormone by an associated cell membrane or an intracellular receptor protein.
  • Nuclear hormone receptors are activated by a lipid-soluble hormone such as estrogen, binding to them inside the cell.
  • Water-soluble hormones, such as epinephrine, bind to a cell-surface localized receptor, initiating a signaling cascade using intracellular second messengers.

• Hormone Receptors

  • A hormone receptor is a molecule that binds to a specific hormone.
  • Receptors for peptide hormones tend to be found on the plasma membrane of cells, whereas receptors for lipid-soluble hormones are usually found within the cytoplasm.
  • The number of these complexes is in turn regulated by the number of hormone or receptor molecules available, and the binding affinity between hormone and receptor.
  • Lipophilic hormones—such as steroid or thyroid hormones—are able to pass through the cell and nuclear membrane; therefore receptors for these hormones do not need to be, although they sometimes are, located in the cell membrane.
  • The thyroid hormone receptor (TR) heterodimerized to the RXR.

• Isotopes in Medicine

  • Nuclear medicine is a medical specialty that involves the application of radioactive substances to diagnose or treat disease.
  • In nuclear medicine procedures, radionuclides are combined with other elements to form chemical compounds.
  • These radiopharmaceuticals, once administered to the patient, can localize to specific organs or cellular receptors.
  • In nuclear medical imaging, radiopharmaceuticals are taken internally, either intravenously or orally.
  • The radiopharmaceuticals used in nuclear medicine therapy emit ionizing radiation that travels only a short distance.

• Replication of Herpes Simplex Virus

  • Herpes replication entails three phases: gene transcription, viral assembly in the nucleus, and budding through the nuclear membrane.
  • The late proteins form the capsid and the receptors on the surface of the virus.
  • The primary envelope is acquired by budding into the inner nuclear membrane of the cell.
  • This then fuses with the outer nuclear membrane releasing a naked capsid into the cytoplasm.
  • Entry of HSV into the host cell involves interactions of several glycoproteins on the surface of the enveloped virus, with receptors on the surface of the host cell.

• Muscle Tone

  • Muscle tone is controlled by neuronal impulses and influenced by receptors found in the muscle and tendons.
  • Connecting to the endomysium of a muscle fiber, muscle spindles are composed of nuclear bag fibers and nuclear chain fibers.
  • However, unlike skeletal muscle fibers where the nuclei are spread out and located at the periphery of the cell, in nuclear bag and nuclear chain fibers the nuclei are located in a central region which is enlarged in nuclear bag fibers.
  • Distinct stretch receptors called golgi tendon organs assess the level of stretch within the tendon.

• The Iranian Nuclear Deal

• Nuclear Proliferation

• Classification of Receptors by Stimulus

  • Sensory receptors can be classified by the type of stimulus that generates a response in the receptor.
  • Sensory receptors perform countless functions in our bodies.
  • Cutaneous receptors are sensory receptors found in the dermis or epidermis.
  • Encapsulated receptors consist of the remaining types of cutaneous receptors.
  • A tonic receptor is a sensory receptor that adapts slowly to a stimulus, while a phasic receptor is a sensory receptor that adapts rapidly to a stimulus.