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Common lipid signaling molecules: lysophosphatidic acid (LPA) sphingosine-1-phosphate (S1P) platelet activating factor (PAF) anandamide or arachidonoyl ethanolamine (AEA). Lipid signaling, broadly defined, refers to any biological cell signaling event involving a lipid messenger that binds a protein target, such as a receptor, kinase or phosphatase, which in turn mediate the effects of these ...
Upon secretion, water-soluble hormones are readily transported through the circulatory system. Lipid-soluble hormones must bond to carrier plasma glycoproteins (e.g., thyroxine-binding globulin (TBG)) to form ligand-protein complexes. Some hormones, such as insulin and growth hormones, can be released into the bloodstream already fully active.
Prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids [1] that have diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are derived enzymatically from the fatty acid arachidonic acid. [2]
Most hormones can be classified as either amino-acid-based hormones (amine, peptide, or protein) or steroid hormones. The former are water-soluble and act on the surface of target cells via second messengers; the latter, being lipid-soluble, move through the plasma membranes of target cells (both cytoplasmic and nuclear) to act within their nuclei.
They usually bind to lipid soluble ligands that diffuse passively through the plasma membrane such as steroid hormones. These ligands bind to specific cytoplasmic transporters that shuttle the hormone-transporter complex inside the nucleus where specific genes are activated and the synthesis of specific proteins is promoted.
Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing energy, signaling, and acting as structural components of cell membranes.
Because peptide hormones and neurotransmitters typically are biochemically hydrophilic molecules, these first messengers may not physically cross the phospholipid bilayer to initiate changes within the cell directly—unlike steroid hormones, which usually do. This functional limitation requires the cell to have signal transduction mechanisms ...
The first identified mechanisms of steroid hormone action were the genomic effects. [12] In this pathway, the free hormones first pass through the cell membrane because they are fat soluble. [7] In the cytoplasm, the steroid may or may not undergo an enzyme-mediated alteration such as reduction, hydroxylation, or aromatization.