Hormonal receptors Adie Kooffreh 0323

objectives  what is a hormone receptors?  Types of hormone receptors  Types of hormones and their different receptors  intracellular and extracellular hormones

Hormone receptors: this is a molecule that can bind to a specific hormones. Receptors for peptide hormones are usually found on the plasma membrane of cells. Lipid-soluble hormones are usually found within the cytoplasm. Upon hormone binding, the receptor can initiate multiple signaling pathways which ultimately lead to changes in the behavior of target cells

Water soluble hormone receptors: – Water-soluble hormones include glycoprotein, catecholamine's and peptide hormones composed of polypeptides, e.g. thyroid-stimulating hormone, follicle-stimulating hormone, leutinizing 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.polypeptidesthyroid-stimulating hormoneleutinizing hormoneinsulindiffuse – The main two types of transmembrane hormone receptor are the G-protein-coupled receptor and the enzyme-coupled receptor. These receptors generally function via intracellular second messengers, including cyclic AMP (cAMP), cyclic GMP (cGMP), inositol 1,4,5-trisphosphate (IP3) and the calcium (Ca 2+ )- calmodulin systemG-protein-coupled receptorsecond messengerscyclic AMPIP3calcium calmodulin

Lipid soluble hormone receptors : – 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.These receptors include those for glucocorticoids,estrogens, androgens, thyroid hormone (T3), calcitriol (the active form of vitamin D), and the retinoids (vitamin A)

Steroid hormone receptors: – steroid hormone receptors are found on the plasma membrane, in the cytosol and also in the nucleus of target cells. They are generally intracellular receptors (typically cytoplasmic) and initiate signal transduction for steroid hormones which lead to changes in gene expression over a time period of hours to days

– Steroid receptors of the nuclear receptor family are all transcription factors. Depending upon the type of receptor, they are either located in the cytosol and move to the cell nucleus upon activation, or remain in the nucleus waiting for the steroid hormone to enter and activate them. This uptake into the nucleus is facilitated by nuclear localization signal (NLS) found in the hinge region of the receptor. This region of the receptor is covered up by heat shock proteins (HSPs) which bind the receptor until the hormone is present. Upon binding by the hormone the receptor undergoes a conformational change releasing the HSP, and the receptor together with the bound hormone enter the nucleus to act upon transcription.

Intracellular receptors – Intracellular receptors are receptors located inside the cell rather than on its cell membrane. Classic hormones that use intracellular receptors include thyroid and steroid hormones.

Laron syndrome – Autosomal recessive disorder characterized by insensitivity to growth hormone. Caused by mutation to the gene encoding for the growth hormone receptors (GHR)

Spontaneous ovarian hyperstimulation syndrome (OHSS) – This is caused a mutation in the FSH receptor.  McCune Albright syndrome, a hereditary disorder characterised by autonomous hyperfunctioning of multiple endocrine tissues (including the thyroid), bony lesions (fibrous dysplasia), and irregulary shaped hyperpigemted skin lesions due to the gsp oncogene

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