Vitamin D independence of small calcium-binding proteins in nonclassical target tissues.
The presence and regulation of Ca-binding proteins (CaBPs) were investigated in newly identified 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] target tissues. 45Ca(2+)-blot analysis of proteins in normal rats yielded a 45Ca2+ band comigrating with authentic calmodulin. Additionally, a parvalbumin-like band (mol mass = 15.4 +/- 0.3 kDa) was prominent in prostate, and a strong unidentified 45Ca2+ band was always evident in the testis (mol mass = 23.5 +/- 0.7 kDa). Lung, bladder, and especially prostate demonstrated 45Ca2+ bands comigrating with the intestinal vitamin D-related CaBP (CaBP-D9K; mol mass = 10.9 +/- 0.5 kDa). Most tissues (including testis, heart, and lung) exhibited low levels of a 45Ca2+ band comigrating with the renal CaBP-D28K (mol mass = 28.3 +/- 0.4 kDa). Importantly, 45Ca2+ binding to all detectable CaBPs was unchanged in these four tissues in vitamin D-deficient rats, despite substantial downregulation of the intestinal CaBP-D9K and renal CaBP-D28K. Neither immunoblot analysis (rabbit anti-rat renal CaBP-D28K) nor Northern analysis (rat brain CaBP-D28K cDNA) provided evidence for coidentity of the 28-kDa 45Ca2+ band with the CaBP-D28K. Conversely, immunoblot analysis of lung, but not prostate, cytosol provided evidence for specific immunocross-reactivity to rabbit anti-rat intestinal CaBP-D9K. Immunoblot analysis of the 9-kDa CaBP in lung further confirmed its vitamin D independence. In conclusion, the vitamin D independence of the CaBPs in these putative new 1,25(OH)2D3 targets suggests the absence of an obligatory relationship between 1,25(OH)2D3 effects and CaBP induction therein.(ABSTRACT TRUNCATED AT 250 WORDS)
Walters
M R
MR
Department of Physiology, Tulane Medical School, New Orleans, Louisiana 70112.
Bruns
M E
ME
Carter
R M
RM
Riggle
P C
PC
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D005260:Female; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008297:Male; D008970:Molecular Weight; D009928:Organ Specificity; D010320:Parvalbumins / Q000302:isolation & purification / Q000378:metabolism; D051381:Rats; D014808:Vitamin D Deficiency / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D010320:Parvalbumins; D002117:Calcitriol; D002118:Calcium