Transglutaminase 2 regulates early chondrogenesis and glycosaminoglycan synthesis.
The expression pattern for tissue transglutaminase (TG2) suggests that it regulates cartilage formation. We analyzed the role of TG2 in early stages of chondrogenesis using differentiating high-density cultures of mesenchymal cells from chicken limb bud as a model. We demonstrate that TG2 promotes cell differentiation towards a pre-hypertrophic stage without inducing precocious hypertrophic maturation. This finding, combined with distinctive up-regulation of extracellular TG2 in the pre-hypertrophic cartilage of the growth plate, indicates that TG2 is an autocrine regulator of chondrocyte differentiation. We also show that TG2 regulates synthesis of the cartilaginous glycosaminoglycan (GAG)-rich extracellular matrix. Elevated levels of TG2 down-regulate xylosyltransferase activity which mediates the key steps in chondroitin sulfate synthesis. On the contrary, inhibition of endogenous transglutaminase activity in differentiating chondrogenic micromasses results in increased GAG deposition and enhancement of early chondrogenic markers. Regulation of GAG synthesis by TG2 appears independent of TGF-β activity, which is a downstream mediator of the TG2 functions in some biological systems. Instead, our data suggest a major role for cAMP/PKA signaling in transmitting TG2 signals in early chondrogenic differentiation. In summary, we demonstrate that matrix synthesis and early stages of chondrogenic differentiation are regulated through a novel mechanism involving TG2-dependent inhibition of PKA. These findings further advance understanding of cartilage formation and disease, and contribute to cartilage bioengineering.
Dept. Biochemistry and Molecular Biology, University of Maryland, School of Medicine, Baltimore, MD 21201, USA.
Dmitry
D
Nurminsky
Shobana
S
Shanmugasundaram
Stephanie
S
Deasey
Claire
C
Michaud
Steven
S
Allen
Doris
D
Hendig
Akbar
A
Dastjerdi
Philippa
P
Francis-West
Maria
M
Nurminskaya
D000818:Animals; D000943:Antigens, Differentiation / Q000378:metabolism; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D002642:Chick Embryo; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism; D020219:Chondrogenesis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015536:Down-Regulation; D005109:Extracellular Matrix / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D006025:Glycosaminoglycans / Q000096:biosynthesis*; D006801:Humans; D018878:Limb Buds / Q000166:cytology / Q000201:enzymology; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010012:Osteogenesis / Q000235:genetics; D010430:Pentosyltransferases / Q000235:genetics; D011401:Promoter Regions, Genetic; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011993:Recombinant Fusion Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D051785:Smad Proteins / Q000235:genetics; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000378:metabolism; D011503:Transglutaminases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D014921:Wings, Animal / Q000196:embryology / Q000378:metabolism; D000097608:UDP Xylose-Protein Xylosyltransferase
D000943:Antigens, Differentiation; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins; D006025:Glycosaminoglycans; D008156:Luciferases; D020928:Mitogen-Activated Protein Kinases; D010430:Pentosyltransferases; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011993:Recombinant Fusion Proteins; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; D011503:Transglutaminases; D000097608:UDP Xylose-Protein Xylosyltransferase