title: Biological role of prolyl 3-hydroxylation in type IV collagen.
abstract: Collagens constitute nearly 30% of all proteins in our body. Type IV collagen is a major and crucial component of basement membranes. Collagen chains undergo several posttranslational modifications that are indispensable for proper collagen function. One of these modifications, prolyl 3-hydroxylation, is accomplished by a family of prolyl 3-hydroxylases (P3H1, P3H2, and P3H3). The present study shows that P3H2-null mice are embryonic-lethal by embryonic day 8.5. The mechanism of the unexpectedly early lethality involves the interaction of non-3-hydroxylated embryonic type IV collagen with the maternal platelet-specific glycoprotein VI (GPVI). This interaction results in maternal platelet aggregation, thrombosis of the maternal blood, and death of the embryo. The phenotype is completely rescued by producing double KOs of P3H2 and GPVI. Double nulls are viable and fertile. Under normal conditions, subendothelial collagens bear the GPVI-binding sites that initiate platelet aggregation upon blood exposure during injuries. In type IV collagen, these sites are normally 3-hydroxylated. Thus, prolyl 3-hydroxylation of type IV collagen has an important function preventing maternal platelet aggregation in response to the early developing embryo. A unique link between blood coagulation and the ECM is established. The newly described mechanism may elucidate some unexplained fetal losses in humans, where thrombosis is often observed at the maternal/fetal interface. Moreover, epigenetic silencing of P3H2 in breast cancers implies that the interaction between GPVI and non-3-hydroxylated type IV collagen might also play a role in the progression of malignant tumors and metastasis.
authors.affiliation: Research Department, Shriners Hospitals for Children, Portland, OR 97239.
authors.forename: Elena
authors.initials: E
authors.lastname: Pokidysheva
authors.forename: Sergei
authors.initials: S
authors.lastname: Boudko
authors.forename: Janice
authors.initials: J
authors.lastname: Vranka
authors.forename: Keith
authors.initials: K
authors.lastname: Zientek
authors.forename: Kerry
authors.initials: K
authors.lastname: Maddox
authors.forename: Markus
authors.initials: M
authors.lastname: Moser
authors.forename: Reinhard
authors.initials: R
authors.lastname: Fässler
authors.forename: Jerry
authors.initials: J
authors.lastname: Ware
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Bächinger
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001777:Blood Coagulation; D002417:Cattle; D024141:Collagen Type IV / Q000737:chemistry / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D006900:Hydroxylation; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D010641:Phenotype; D010974:Platelet Aggregation; D011393:Procollagen-Proline Dioxygenase / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D013927:Thrombosis; D013997:Time Factors
chemical_list: D024141:Collagen Type IV; D011393:Procollagen-Proline Dioxygenase; C586944:LEPREL1 protein, mouse; C568061:P3H2 protein, human; C030606:proline, 2-oxoglutarate 3-dioxygenase