<P> Hormone receptors can behave as transcription factors by interacting directly with DNA or by cross-talking with signaling pathways . This process is mediated through co-regulators . In the absence of ligand, receptor molecules bind corepressors in order to repress gene expression, compacting chromatin through histone deacetylatase . When a ligand is present, nuclear receptors undergo a conformational change to recruit various coactivators . These molecules work to remodel chromatin . Hormone receptors have highly specific motifs which are able to interact with coregulator complexes . This is the mechanism through which receptors can induce regulation of gene expression depending on both the extracellular environment and the immediate cellular composition . Steroid hormones and their regulation by receptors are the most potent molecule interactions in aiding gene expression . </P> <P> Problems with nuclear receptor binding as a result of shortages of ligand or receptors can have drastic effects on the cell . The dependency on the ligand is the most important part in being able to regulate gene expression, so the absence of ligand is drastic to this process . For example, estrogen deficiency is a cause of osteoporosis and the inability to undergo a proper signaling cascade prevents bone growth and strengthening . Deficiencies in nuclear receptor - mediated pathways play a key role in the development of disease, like osteoporosis . </P> <P> Water - soluble hormones include glycoproteins, catecholamines, and peptide hormones composed of polypeptides, e.g. thyroid - stimulating hormone, follicle - stimulating hormone, luteinizing 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 because they have bound to a receptor protein located on the plasma membrane . </P> <P> Water - soluble hormones come from amino acids and are located and stored in endocrine cells until actually needed . </P>

Where are receptors for water soluble hormones located