Selected-GenAtlas references SOURCE GeneCards NCBI Gene Swiss-Prot Orphanet Ensembl
HGNC UniGene Nucleotide OMIM UCSC
Home Page
Symbol PRG4 contributors: mct/npt - updated : 21-12-2016
HGNC name proteoglycan 4
HGNC id 9364
Corresponding disease
CACP camptodactyly- arthropathy-coxa varapericarditis syndrome
Location 1q31.1      Physical location : 186.265.404 - 186.283.686
Synonym name
  • lubricin
  • megakaryocyte stimulating factor
  • proteoglycan 4, (megakaryocyte stimulating factor, articular superficial zone protein, camptodactyly, arthropathy, coxa vara, pericarditis syndrome)
  • bG174L6.2 (MSF: megakaryocyte stimulating factor)
  • articular superficial zone protein
  • superficial zone proteoglycan
  • Synonym symbol(s) MSF, SZP, HAPO, JCAP, bG174L6.2, FLJ32635, CACP
    TYPE functioning gene
    STRUCTURE 18.28 kb     13 Exon(s)
    Genomic sequence alignment details
    10 Kb 5' upstream gene genomic sequence study
    MAPPING cloned Y linked N status provisional
    Physical map
    RGS16 1q25-q31 regulator of G-protein signalling 16 RGS8 1q25-q31 regulator of G-protein signalling 8 NPL 1q25 N-acetylneuraminate pyruvate lyase (dihydrodipicolinate synthase) DHX9 1q25 DEAH (Asp-Glu-Ala-His) box polypeptide 9 C1orf14 1q25-q31 chromosome 1 open reading frame 14 LOC391143 1 similar to natural cytotoxicity triggering receptor 1; lymphocyte antigen 94 (mouse) homolog (activating NK-receptor; NK-p46); lymphocyte antigen 94 (mouse) homolog (activating NK-receptor ; NK-p46); lymphocyte antigen 94 homolog, a LOC343326 1q25.2 similar to Keratin, type I cytoskeletal 18 (Cytokeratin 18) (K18) (CK 18) LAMC1 1q31 laminin, gamma 1 (formerly LAMB2) LAMC2 1q25-q31 laminin, gamma 2 NMNAT2 1q25-q31 nicotinamide nucleotide adenylyltransferase 2 C1orf16 1q25-q31 chromosome 1 open reading frame 16 NCF2 1q25 neutrophil cytosolic factor 2 (65kDa, chronic granulomatous disease, autosomal 2) ARPC5 1q25.2 actin related protein 2/3 complex, subunit 5, 16kDa RGL 1q25.2 actin related protein 2/3 complex, subunit 5, 16kDa C1orf17 1q25-q31 chromosome 1 open reading frame 17 C1orf19 1q25-q31 chromosome 1 open reading frame 19 LOC391144 1 similar to Rho-GTPase-activating protein 8 C1orf21 1q25-q31 chromosome 1 open reading frame 21 C1orf22 1q24-q25 chromosome 1 open reading frame 22 C1orf24 1q25-q31 chromosome 1 open reading frame 24 RNF2 1q25.1 ring finger protein 2 C1orf25 1q25.2 chromosome 1 open reading frame 25 C1orf26 1q25 chromosome 1 open reading frame 26 IVNS1ABP 1q25.1-q31.1 influenza virus NS1A binding protein FIBL-6 1q25.3 hemicentin PRG4 1q25-q31 proteoglycan 4, (megakaryocyte stimulating factor, articular superficial zone protein, camptodactyly, arthropathy, coxa vara, pericarditis syndrome) TPR 1q25 translocated promoter region (to activated MET oncogene) C1orf27 1q25-q31 translocated promoter region (to activated MET oncogene) PDC 1q32-q41 phosducin LOC391145 1 similar to KIAA1871 protein PTGS2 1q25.2-q25.3 prostaglandin-endoperoxide synthase 2 (prostaglandin G/H synthase and cyclooxygenase) PLA2G4A 1q25 phospholipase A2, group IVA (cytosolic, calcium-dependent) LOC343332 1q25.3 similar to Farnesyl pyrophosphate synthetase (FPP synthetase) (FPS) (Farnesyl diphosphate synthetase)
    TRANSCRIPTS type messenger
    identificationnb exonstypebpproduct
    ProteinkDaAAspecific expressionYearPubmed
    13 - 5059 - 1404 - 2013 23599181
    exon 1-6
    12 splicing 4936 - 1363 same as PRG4A 2013 23599181
    skipping exon 2
    11 splicing 4780 - 1311 same as A + catilage 2013 23599181
    skipping exon 4 and 5
    10 splicing 4657 - 1270 predominantly in cartilage 2013 23599181
    skipping exon 2, 4, 5
    13 - 4921 - 1361 - 2013 23599181
    Type widely
       expressed in (based on citations)
    SystemOrgan level 1Organ level 2Organ level 3Organ level 4LevelPubmedSpeciesStageRna symbol
     thymus   highly
    Reproductivefemale systemuteruscervix highly
     male systemprostate  highly
    Skeletonappendicularjoint    Homo sapiens
    SystemTissueTissue level 1Tissue level 2LevelPubmedSpeciesStageRna symbol
    Connectiveadipose  highly
    Connectivecartilagefibrocartilage   Homo sapiens
    SystemCellPubmedSpeciesStageRna symbol
    not specificsynoviocyte Homo sapiens
    cell lineage
    cell lines
    at STAGE
    physiological period fetal, pregnancy
    Text placenta, spleen
  • N terminal somatomedin B-like domain
  • heparin binding site
  • chondroitin sulfate attachment site
  • oloigosaccharide attachment sites
  • mucin-like repeat in the central region
  • a C terminal T rich region
  • conjugated GlycoP
    FAMILY plasticity-related gene family
    CATEGORY regulatory , secretory
        plasma membrane
    basic FUNCTION
  • regulator of ossification
  • regulator of intimal cell growth
  • mucin-like proteoglycan that is a major lubricant in articulating joints
  • superficial zone protein (SZP), an important joint lubricant produced by superficial zone, that are more responsive to stimulation by catabolic cytokines such as IL1 (Taniguchi 2009)
  • synovial glycoprotein that has been shown to be a boundary lubricant (Gleghorn 2009)
  • brain-specific integral membrane protein implicated in neuronal plasticity, such as filopodia formation and axon growth after brain lesion (Broggini 2010)
  • having lubricating and protective actions in joints
  • critical protective factor in articular joints, is implicated in hematopoietic progenitor cell expansion and megakaryopoiesis
  • may have a role in normal disc posterior attachment physiology through the prevention of cellular adhesion as well as providing lubrication during normal bilaminar zone function
  • is likely able to bind to polymorphonuclear granulocytes (PMN) via an L-selectin-dependent and -independent manner and may play a role in PMN-mediated inflammation
  • PRG4 presence significantly reduces friction between the cornea and conjunctiva and its deficiency may play a role in promoting corneal damage
  • important role of PRG4 in mediating interactions at the cartilage surface is to attach to the cartilage surface
  • PRG4 (lubricin) is a novel putative ligand for CD44 and may control synoviocyte overgrowth in inflammatory arthropathies via a CD44-mediated mechanism
  • mucinous glycoprotein secreted by synovial fibroblasts and superficial zone chondrocytes, that has a homeostatic multifaceted role in the joint
  • plays an important role in regulating the inflammatory environment under both homeostatic and tissue injury states
  • serves as a lubricant in joints, tendons and visceral cavities (pleural cavity, pericardium) and inhibits synovial proliferation
  • plays a role in controlling inflammation and pain as well as being a mechanical lubricant
  • adult talar cartilage increases both the PRG4 release and biosynthetic activity as an immediate cellular response to injury
  • CELLULAR PROCESS cell life, differentiation
    cell life, proliferation/growth
    text ossification
    a component
    small molecule
  • PRG4 is a PTH-responsive gene in bone and liver
  • is a dynamic regulator of skeletogenesis and PTH skeletal anabolism
  • is a novel PTH-responsive factor regulating immune cells and PTH actions on marrow hematopoietic progenitor cells
  • PRG4 binds to TLR2 and TLR4 and this binding mediates a novel anti-inflammatory role for PRG4
  • may play a role in modulating inflammatory responses through interaction with CD44
  • cell & other
    corresponding disease(s) CACP
    Other morbid association(s)
    TypeGene ModificationChromosome rearrangementProtein expressionProtein Function
    constitutional     --low  
    in synovial fluid associated with an increase in levels of inflammatory cytokines (Elsaid 2008)
    Variant & Polymorphism
    Candidate gene
  • association of PRG4 concentration in synovial fluid and clinical status of osteoarthritic knee
  • Therapy target
    supplementation of synovial fluid with PRG4 may be an effective treatment to prevent cartilage deterioration in patients with genetic or acquired deficiency of PRG4
  • adult Prg4 mutant mice had decreased trabecular and cortical bone, and blunted PTH-mediated increases in bone mass