The role of plasma-binding proteins in the cellular uptake of lipophilic vitamins and steroids.
Steroid hormones and many other lipophilic compounds are believed to enter cells solely by free diffusion through the plasma membrane. However, recent work using a megalin-deficient mouse model has identified a new endocytic pathway responsible for the delivery of steroids to renal and gonadal tissues. This review describes these new pathways for uptake of 25-hydroxy-vitamin-D3 and the gonadal sex-steroids (17beta-estradiol and testosterone) bound to vitamin D-binding protein and sex hormone-binding globulin respectively. Furthermore examples of other lipophilic molecules that enter cells by receptor-mediated pathways will be presented and the receptors responsible for their uptake described.
Andreassen
T K
TK
Department of Medical Biochemistry, University of Aarhus, Denmark. tka@biokemi.au.dk
D000818:Animals; D004285:Dogs; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D011247:Pregnancy; D011485:Protein Binding; D011817:Rabbits; D051381:Rats; D012712:Serum Globulins / Q000378:metabolism; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism*; D015398:Signal Transduction; D013256:Steroids / Q000378:metabolism*; D014809:Vitamin D-Binding Protein / Q000097:blood; D014815:Vitamins / Q000378:metabolism*
D012712:Serum Globulins; D012738:Sex Hormone-Binding Globulin; D013256:Steroids; D014809:Vitamin D-Binding Protein; D014815:Vitamins