Steroid synthesis pathway mnemonic

Biosynthesis of steroid hormones requires a battery of oxidative enzymes located in both mitochondria and endoplasmic reticulum. The rate-limiting step in this process is the transport of free cholesterol from the cytoplasm into mitochondria. Within mitochondria, cholesterol is converted to pregnenolone by an enzyme in the inner membrane called CYP11A1. Pregnenolone itself is not a hormone, but is the immediate precursor for the synthesis of all of the steroid hormones. The following table delineates the enzymes required to synthesize the major classes of steroid hormones.

The first three control mechanisms are exerted by cholesterol itself. Cholesterol acts as a feed-back inhibitor of pre-existing HMGR as well as inducing rapid degradation of the enzyme. The latter is the result of cholesterol-induced polyubiquitination of HMGR and its degradation in the proteosome (see proteolytic degradation below). This ability of cholesterol is a consequence of the sterol sensing domain, SSD of HMGR. In addition, when cholesterol is in excess the amount of mRNA for HMGR is reduced as a result of decreased expression of the gene. The mechanism by which cholesterol (and other sterols) affect the transcription of the HMGR gene is described below under regulation of sterol content .

Dexamethasone and largazole cooperate to suppress invasion and to restore E-cadherin localization to the cell peripher y. ( a) Phase contrast micrographs showing morphological changes in MDA-MB-231 cells induced by E-cadherin expression combined with 100 nM dexamethasone and 10 nM largazole treatments. Insets show the cells at higher magnification. (b ) Fluorescence (E-Cad-GFP) or immunofluorescence microscopy (g -catenin (g-Cat.)) of 231/E-Cad-GFP cells treated for 72 h with vehicle (Control), 100 n M dexamethasone, 10 nM largazole or 100 nM dexamethasone + 10 nM largazole (Dex. + Larg.). (c ) Invasion assays were per formed with the indicated cell lines treated for 72 h with or without 100 nM dexamethasone + 10 nM largazole using modified Boyden chambers impregnated with matrigel. The results are presented as the average number of cells that invaded through the membrane per field . of five randomly chosen fields, and are representative of three independently per formed experiments.

How might behaviors affect hormones? The birdsong example demonstrates how hormones can affect behavior, but as noted, the reciprocal relation also occurs; that is, behavior can affect hormone concentrations. For example, the sight of a territorial intruder may elevate blood testosterone concentrations in resident male birds and thereby stimulate singing or fighting behavior. Similarly, male mice or rhesus monkeys that lose a fight decrease circulating testosterone concentrations for several days or even weeks afterward. Comparable results have also been reported in humans. Testosterone concentrations are affected not only in humans involved in physical combat, but also in those involved in simulated battles. For example, testosterone concentrations were elevated in winners and reduced in losers of regional chess tournaments.

Steroid synthesis pathway mnemonic

steroid synthesis pathway mnemonic

How might behaviors affect hormones? The birdsong example demonstrates how hormones can affect behavior, but as noted, the reciprocal relation also occurs; that is, behavior can affect hormone concentrations. For example, the sight of a territorial intruder may elevate blood testosterone concentrations in resident male birds and thereby stimulate singing or fighting behavior. Similarly, male mice or rhesus monkeys that lose a fight decrease circulating testosterone concentrations for several days or even weeks afterward. Comparable results have also been reported in humans. Testosterone concentrations are affected not only in humans involved in physical combat, but also in those involved in simulated battles. For example, testosterone concentrations were elevated in winners and reduced in losers of regional chess tournaments.

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