A poorly understood collagen post-translational modification has been 3-prolyl-hydroxylation (P3H) converting proline to 3-hydroxy proline (3-Hyp). It occurs in the fibrillar collagens, i.e., types I, II and III collagen, at only 1 proline position, but abundantly in other collagens such as network collagens, i.e., type IV collagen, where it occurs in up to 10% of residues. This begs the question of whether 3-Hyp residues serve divergent biological functions in different settings and tissues. In recent data, we have identified a novel protein, CRTAP or Cartilage Associated Protein, that is representative of the Leprecan family of proteins recently reported to contain a conserved 2-oxoglutarate dioxygenase domain that is found in collagen 4-prolyl-hydroxylases (P4Hs), Hypoxic Inducible Factor (HIF) 4-prolyl-hydoxylases (PDHs), and lysyl hydroxylases (PLODs). Moreover, Leprecan or P3H1 has collagen 3-prolyl-hydroxylase activity in vitro implicating this family of genes as the long sought after PSH's. By combining human and mouse genetic, and proteomic approaches, we show (see Preliminary Studies C.1.) that loss of Crtap in mice causes an osteochondrodysplasia characterized by short stature, kyphosis, and severe osteoporosis. Moreover, this phenotype is biochemically associated with conversion of the single 3-hydroxy-proline to proline in the triple helical domain of types I and II collagen. CRTAP can bind P3H1 and is required for P3H activity in vivo. This data raises important mechanistic questions that we will address in our Specific Aims. 1) Are the phenotypic features of Crtap loss of function due solely to loss of 3-prolyl-hydroxylation of fibrillar collagens? 2) What are the consequences of 3-Hyp loss in cartilage and bone on cellular differentiation and function, and collagen biosynthesis? 3) What is the human clinical spectrum associated with loss of 3-prolyl-hydroxylation of fibrillar collagens? 4) What regulates the context- dependent function of CRTAP? These questions address what we believe to be a new area in matrix biology and pathogenesis of skeletal dysplasias, i.e., the in vivo phenotypic and biochemical consequences of dysregulation of the 3-prolyl-hydroxylation machinery. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE017713-02
Application #
7252537
Study Section
Skeletal Biology Structure and Regeneration Study Section (SBSR)
Program Officer
Scholnick, Steven
Project Start
2006-08-01
Project End
2011-04-30
Budget Start
2007-05-01
Budget End
2008-04-30
Support Year
2
Fiscal Year
2007
Total Cost
$115,398
Indirect Cost
Name
Baylor College of Medicine
Department
Genetics
Type
Schools of Medicine
DUNS #
051113330
City
Houston
State
TX
Country
United States
Zip Code
77030
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