Cartilage glycoprotein 39

chondrex, or chitinase 3-like 1 (CHI3L1), Cartilage glycoprotein-39 (gp-39)or Chondrocyte protein YKL-40 is one of the major secreted proteins of ex vivo cultured human articular chondrocytes, synovial cells, and macrophages and also expressed by mature neutrophils (from myelocyte-metamyelocyte stage). High levels of YKL-40 are found in synovial fluid from patients with active rheumatoid arthritis (RA) and in the hippocampus of schizophrenic patients [AU: Carmen Chung, Teresa Tallerico, Philip SeemanTI: Schizophrenia hippocampus has elevated expression of chondrex glycoprotein geneSO: SynapseVL: 50NO: 1PG: 29-34YR: 2003CP: Copyright © 2003 Wiley-Liss, Inc.ON: 1098-2396PN: 0887-4476AD: Department of Pharmacology, Toronto, Ontario, Canada; Department of Psychiatry, University of Toronto, Toronto, CanadaDOI: 10.1002/syn.10228US: http://dx.doi.org/10.1002/syn.10228] . YKL-40 belongs to the 18-glycosyl hydrolase (mammalian chitinase) family, and is one of the putative autoantigens in rheumatoid arthritis (RA). High levels of YKL-40 are found in synovial fluid from patients with active RA. The name 'YKL' stands for its N-terminal tripeptide sequence, and unlike the other member YKL39 (CHITINASE 3-LIKE 2 or CHI3L2; CHONDROCYTE PROTEIN 39) which is unglycosylated, YKL40 is glycosylated. Unlike YKL-40, YKL39 is upregulated in Osteoarthritis but not in rheumatoid arthritis [ Knorr, T, Obermayr, F, Bartnik, E, Zien, A, Aigner, TYKL-39 (chitinase 3-like protein 2), but not YKL-40 (chitinase 3-like protein 1), is up regulated in osteoarthritic chondrocytesAnn Rheum Dis 2003 62: 995-998] .

Though its function is not clearly understood yet, its most likely function is related to remodeling or degradation of the extracellular matrix. It is also supposed to act as a cellular survival (anti-apoptotis), cell growth and migration factor in response to various types of physiologic stress, such as inflammation, hypoxia, and nutrient deprivation, possibly acts by its inhibition of the stress sensor enzyme MAP3K5 (APOPTOSIS SIGNAL-REGULATING KINASE 1, ASK1). In Neutrophils YKL-40 was found to colocalize and comobilize with lactoferrin in the "specific granules".

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