Structure-function studies of 1,25-dihydroxyvitamin D3 and the vitamin D endocrine system. 1,25-dihydroxy-pentadeuterio-previtamin D3 (as a 6-s-cis analog) stimulates nongenomic but not genomic biological responses.
The hormone 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) generates biological responses via both genomic and nongenomic mechanisms. This article addresses activity differences between the 6-s-trans (extended) and the 6-s-cis (steroid-like) conformation of 1,25-(OH)2D3 to initiate these responses. Because of facile interconversion of the 6-s-trans and 6-s-cis conformers of 1,25-(OH)2D3, kinetically competent amounts of both conformers exist to interact with any potential receptors for 1,25-(OH)2D3. We have chemically synthesized 1,25-(OH)2-9,14,19,19,19-pentadeuterio-pre-D3 (1,25-(OH)2-d5-pre-D3), an analog of the 6-s-cis conformation of 1,25-(OH)2D3. We found that 1,25-(OH)2-d5-pre-D3 and 1,25-(OH)2D3 were equivalently active in two nongenomic systems (transcaltachia as measured in the perfused chick intestine and 45Ca2+ uptake through voltage-gated Ca2+ channels in ROS 17/2.8 cells). 1,25-(OH)2-d5-pre-D3 was significantly less active both in binding in vitro to the plasma vitamin D-binding protein (7%) and to the chick (10%) and pig (4%) intestinal nuclear 1,25-(OH)2D3 receptors generating genomic biological responses in vivo (induction of plasma levels of osteocalcin, < 5%) or in cultured cells (inhibition of HL-60 cell differentiation, < 5%; inhibition of MG-63 proliferation, < 2%; and induction of osteocalcin, < 2%). These results suggest that the genomic and nongenomic responses are mediated by separate receptors. Further, the 6-s-cis form (steroid-like conformation) of the natural hormone, 1,25-(OH)2D3, may be selectively responsible for its nongenomic function(s).
Norman
A W
AW
Department of Biochemistry, University of California, Riverside 92521.
Okamura
W H
WH
Farach-Carson
M C
MC
Allewaert
K
K
Branisteanu
D
D
Nemere
I
I
Muralidharan
K R
KR
Bouillon
R
R
D000818:Animals; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002645:Chickens; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007700:Kinetics; D015473:Leukemia, Promyelocytic, Acute; D008297:Male; D015675:Osteocalcin / Q000096:biosynthesis; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000187:drug effects / Q000378:metabolism; D013329:Structure-Activity Relationship; D013552:Swine; D014407:Tumor Cells, Cultured; D014809:Vitamin D-Binding Protein / Q000378:metabolism
D015220:Calcium Channels; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D014809:Vitamin D-Binding Protein; D015675:Osteocalcin; C025169:1,25-dihydroxy-previtamin D(3); D002117:Calcitriol; D002118:Calcium