This application proposes to investigate the vitamin D receptor (VDR) and to examine its role in the action of 1,25-dihydroxyvitamin D3 (1,25D), the active form of vitamin D. The focus of the proposal is the study of the VDR and various other cellular factors that modulate the amplitude and nature of the target tissue responses to 1,25D. 1,25D responsiveness may be increased or decreased by a variety of cellular mechanisms, yielding a spectrum of activity in target cells from highly sensitive to totally resistant.
Three Specific Aims are to be addressed in the investigation of factors that contribute to the regulation of 1,25D responsiveness.
Specific Aim I will probe into the genetic mechanisms of target organ resistance due to mutations in the VDR. It will examine a number of new families with the syndrome of target organ resistance to 1,25D, Hereditary Vitamin D Resistant Rickets (HVDRR), and elucidate the nature of the mutations in the VDR gene. In addition, it will determine whether 1,25D- independent activation of target genes is the mechanism by which some HVDRR children """"""""outgrow"""""""" their disease.
Specific Aim II will investigate the role of proteins that interact with the VDR (VDR- Interacting Proteins or DRIPs) in mediating 1,25D action. Three areas in which DRIPs will be studied include: 1) a search for new and unknown DRIPs employing the GAL4 Two-Hybrid System; 2) investigation by mutational and functional analyses of various aspects of the interaction of VDR with the retinoid X receptor (RXR), with which it is known to heterodimerize to transactivate target genes; 3) exploration of the role of calreticulin, a protein recently shown to inhibit the action of other steroid receptors and that of VDR (as shown by the applicants' preliminary data).
Specific Aim III will study the physiological mechanisms by which VDR abundance and function is modulated by retinoids, glucocorticoids and estrogens. Special attention will be addressed to the prostate gland and prostate cancer cells. There are many health- related aspects of the project including:
for Aim I, the elucidation of mutations in HVDRR families and providing genetic counseling, as well as delineating the mechanisms by which some children with HVDRR """"""""outgrow"""""""" their genetic defect and heal their rickets;
for Aim II, investigating multiple factors that modulate 1,25 responsiveness in normal cells and potentially in various disease states; and for Aim III, exploration of the interaction of 1,25 with retinoids, estrogens and glucocorticoids, all of which have been used to treat prostate cancer, to determine whether an enhancement of the beneficial effects of 1,25D can be achieved in the therapy of prostate cancer. Overall, the grant request is a multi-faceted analysis of the role of VDR in 1,25D action in various states of health and disease, emphasizing the themes of genetic and physiological regulation of hormone responsiveness.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
3R01DK042482-08S1
Application #
6084173
Study Section
Orthopedics and Musculoskeletal Study Section (ORTH)
Program Officer
Margolis, Ronald N
Project Start
1999-06-01
Project End
2001-05-31
Budget Start
1999-06-01
Budget End
2000-05-31
Support Year
8
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Stanford University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
800771545
City
Stanford
State
CA
Country
United States
Zip Code
94305
Malloy, Peter J; Tasic, Velibor; Taha, Doris et al. (2014) Vitamin D receptor mutations in patients with hereditary 1,25-dihydroxyvitamin D-resistant rickets. Mol Genet Metab 111:33-40
Huang, Karen; Malloy, Peter; Feldman, David et al. (2013) Enteral calcium infusion used successfully as treatment for a patient with hereditary vitamin D resistant rickets (HVDRR) without alopecia: a novel mutation. Gene 512:554-9
Sequeira, Vanessa B; Rybchyn, Mark S; Tongkao-On, Wannit et al. (2012) The role of the vitamin D receptor and ERp57 in photoprotection by 1?,25-dihydroxyvitamin D3. Mol Endocrinol 26:574-82
Malloy, Peter J; Zhou, Yulin; Wang, Jining et al. (2011) Hereditary vitamin D-resistant rickets (HVDRR) owing to a heterozygous mutation in the vitamin D receptor. J Bone Miner Res 26:2710-8
Malloy, Peter J; Feldman, David (2011) The role of vitamin D receptor mutations in the development of alopecia. Mol Cell Endocrinol 347:90-6
Aljubeh, Jamal M; Wang, Jining; Al-Remeithi, Sareea S et al. (2011) Report of two unrelated patients with hereditary vitamin D resistant rickets due to the same novel mutation in the vitamin D receptor. J Pediatr Endocrinol Metab 24:793-9
Krishnan, Aruna V; Feldman, David (2010) Molecular pathways mediating the anti-inflammatory effects of calcitriol: implications for prostate cancer chemoprevention and treatment. Endocr Relat Cancer 17:R19-38
Malloy, Peter J; Feldman, David (2010) Genetic disorders and defects in vitamin d action. Endocrinol Metab Clin North Am 39:333-46, table of contents
Forghani, Nikta; Lum, Catherine; Krishnan, Sowmya et al. (2010) Two new unrelated cases of hereditary 1,25-dihydroxyvitamin D-resistant rickets with alopecia resulting from the same novel nonsense mutation in the vitamin D receptor gene. J Pediatr Endocrinol Metab 23:843-50
Malloy, Peter J; Wang, Jining; Srivastava, Tarak et al. (2010) Hereditary 1,25-dihydroxyvitamin D-resistant rickets with alopecia resulting from a novel missense mutation in the DNA-binding domain of the vitamin D receptor. Mol Genet Metab 99:72-9

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