DMP1 (dentin matrix acidic phosphoprotein 1) is a secreted, highly acidic, intrinsically disordered phosphoprotein of the SIBLING family (small integrin-binding ligand, N-linked glycoproteins), encoded in the SIBLING cluster on chromosome 4q21. It is expressed by odontoblasts, osteoblasts and above all by osteocytes, and is deposited in the mineralized extracellular matrix of bone and dentin, largely as proteolytically processed N-terminal (proteoglycan) and C-terminal phosphorylated fragments. Its serine-rich acidic domains are phosphorylated in the secretory pathway, notably by the Golgi casein kinase FAM20C, and bind calcium; in vitro the protein and its C-terminal fragment nucleate hydroxyapatite, while the intact phosphorylated protein and the N-terminal domain can inhibit crystal growth, so DMP1 is regarded as a matrix regulator of biomineralization. It also carries an RGD motif and engages alphaVbeta3 integrin. Loss of DMP1 in mice and humans causes defective osteocyte maturation, hypomineralized bone and dentin, and elevated osteocytic FGF23 expression with renal phosphate wasting (autosomal recessive hypophosphatemic rickets type 1), indicating that DMP1 is also required, by a still undefined mechanism, to restrain FGF23 production. A nuclear, transcriptional role in pre-osteoblasts has been proposed but is less firmly established.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0001503 ossification | IEA GO_REF:0000002 | MODIFY | Summary: InterPro-domain inference of ossification for the DMP1 family. Reason: DMP1 participates in skeletal mineralization rather than ossification in the broad developmental sense; loss of DMP1 produces hypomineralized bone and osteomalacia, while bone is still formed. The supported, more specific process is bone mineralization, in which DMP1 contributes calcium-binding and hydroxyapatite-nucleating matrix activity. Proposed replacements: bone mineralization Supporting Evidence: PMID:17033621 when deleted in mice, results in a hypomineralized bone phenotype PMID:12952204 DMP1 could be considered as a nucleator for apatite deposition in vitro |
| GO:0001503 ossification | TAS PMID:8509401 Characterization of a novel dentin matrix acidic phosphoprot... | MODIFY | Summary: Author statement (1993 cloning paper) linking the dentin acidic phosphoprotein to mineralization. Reason: The cloning paper proposes a regulatory role in mineralization of dentin matrix, not ossification. Later knockout and patient data support a role in bone mineralization; refine to that process for consistency with the IEA row. Proposed replacements: bone mineralization Supporting Evidence: PMID:8509401 a matrix-associated acidic phosphoprotein, with a potentially high calcium ion binding capacity PMID:17033621 when deleted in mice, results in a hypomineralized bone phenotype |
| GO:0005178 integrin binding | TAS PMID:8509401 Characterization of a novel dentin matrix acidic phosphoprot... | KEEP AS NON CORE | Summary: Integrin binding inferred from the RGD motif; corroborated by Reactome alphaVbeta3 event. Reason: The cited 1993 paper only notes an RGD integrin-binding sequence. Reactome curates DMP1 engagement of alphaVbeta3 integrin, which is plausible for a SIBLING protein, but the signalling role is secondary to the matrix mineralization function; retain as non-core. Supporting Evidence: PMID:8509401 AG1 contains single RGD integrin binding and N-glycosylation sequences Reactome:R-HSA-4086200 DMP1 acts via interaction with alphaVbeta3 integrin |
| GO:0005509 calcium ion binding | EXP PMID:32190922 Functional derivatives of human dentin matrix protein 1 modu... | ACCEPT | Summary: Experimental calcium binding by human DMP1 fragments (calcium sequestration, Ca-dependent oligomerization). Reason: Calcium binding by the acidic, phosphorylated domains is the molecular basis of DMP1 action in biomineralization and is shown directly for human DMP1 fragments and recombinant protein. Supporting Evidence: PMID:32190922 they sequester the calcium ions during the calcite formation PMID:12952204 recombinant DMP1 (rDMP1) possesses calcium-binding ability under physiological conditions |
| GO:0005509 calcium ion binding | TAS PMID:8509401 Characterization of a novel dentin matrix acidic phosphoprot... | ACCEPT | Summary: Calcium binding stated in the cloning paper from composition; consistent with later experiments. Reason: The TAS assertion is a compositional inference, but direct 45Ca-binding data confirm it; consistent with the EXP row. Supporting Evidence: PMID:8509401 a matrix-associated acidic phosphoprotein, with a potentially high calcium ion binding capacity PMID:12952204 recombinant DMP1 (rDMP1) possesses calcium-binding ability under physiological conditions |
| GO:0005576 extracellular region | TAS Reactome:R-HSA-4086200 | ACCEPT | Summary: Secreted extracellular protein (Reactome). Reason: DMP1 is a secreted matrix protein; extracellular region is correct though less specific than extracellular matrix. Supporting Evidence: Reactome:R-HSA-4086200 DMP1 acts via interaction with alphaVbeta3 integrin PMID:12615915 This phosphorylated DMP1 is then exported out into the extracellular matrix, where it regulates nucleation of hydroxyapatite |
| GO:0005634 nucleus | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: Electronic transfer of a nuclear localization reported for undifferentiated osteoblasts. Reason: Nuclear DMP1 in pre-osteoblasts with a proposed transcriptional role is reported by one group; it is not the site of the established matrix function and has not been widely replicated. Retain as non-core. Supporting Evidence: PMID:12615915 In the nucleus, DMP1 acts as a transcriptional component for activation of osteoblast-specific genes like osteocalcin |
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: Electronic transfer of cytoplasmic localization during osteoblast maturation. Reason: Transient cytoplasmic localization accompanies secretion and the reported nucleocytoplasmic shuttling; not a functional site. Non-core. Supporting Evidence: PMID:12615915 This phosphorylated DMP1 is then exported out into the extracellular matrix, where it regulates nucleation of hydroxyapatite |
| GO:0005788 endoplasmic reticulum lumen | TAS Reactome:R-HSA-8952289 | KEEP AS NON CORE | Summary: Reactome places DMP1 in the ER lumen as a FAM20C substrate in the secretory pathway. Reason: DMP1 transits the ER/Golgi lumen where it is phosphorylated by FAM20C before secretion; a correct transit location but not where DMP1 acts. Supporting Evidence: PMID:22582013 Fam20C phosphorylated OPN, MEPE, and DMP1 in a time-dependent manner |
| GO:0030198 extracellular matrix organization | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: IBA propagation of extracellular matrix organization in the DMP1 family. Reason: DMP1 is a matrix component that regulates mineral deposition; there is no evidence that it assembles or organizes the collagenous extracellular matrix. The better-supported process is bone mineralization (see core functions). Supporting Evidence: PMID:12615915 This phosphorylated DMP1 is then exported out into the extracellular matrix, where it regulates nucleation of hydroxyapatite PMID:14769788 in its native form, DMP1 inhibits mineralization, but when cleaved or dephosphorylated, it initiates mineralization |
| GO:0030198 extracellular matrix organization | IEA GO_REF:0000002 | MARK AS OVER ANNOTATED | Summary: InterPro-based extracellular matrix organization. Reason: Same as the IBA row: DMP1 regulates mineral nucleation within the matrix rather than matrix organization. Supporting Evidence: PMID:12615915 This phosphorylated DMP1 is then exported out into the extracellular matrix, where it regulates nucleation of hydroxyapatite |
| GO:0031012 extracellular matrix | IBA GO_REF:0000033 | ACCEPT | Summary: DMP1 is a component of the mineralized extracellular matrix (IBA). Reason: Well established; DMP1 is deposited in bone and dentin matrix. Supporting Evidence: PMID:12615915 This phosphorylated DMP1 is then exported out into the extracellular matrix, where it regulates nucleation of hydroxyapatite |
| GO:0031012 extracellular matrix | IEA GO_REF:0000107 | ACCEPT | Summary: Ortholog transfer of extracellular matrix localization. Reason: Consistent with the human and rodent data. Supporting Evidence: PMID:12615915 This phosphorylated DMP1 is then exported out into the extracellular matrix, where it regulates nucleation of hydroxyapatite |
| GO:0031012 extracellular matrix | TAS PMID:8509401 Characterization of a novel dentin matrix acidic phosphoprot... | ACCEPT | Summary: Extracellular matrix localization from the original dentin protein characterization. Reason: Correct; the protein was identified from dentin matrix. Supporting Evidence: PMID:8509401 a matrix-associated acidic phosphoprotein, with a potentially high calcium ion binding capacity |
| GO:0050840 extracellular matrix binding | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: IBA extracellular matrix binding. Reason: DMP1 associates with collagen/mineralized matrix and binds hydroxyapatite-forming calcium phosphate, so matrix binding is plausible, but the core activity is calcium binding/mineral nucleation. Non-core. Supporting Evidence: PMID:14769788 in its native form, DMP1 inhibits mineralization, but when cleaved or dephosphorylated, it initiates mineralization |
| GO:0050840 extracellular matrix binding | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Ortholog transfer of extracellular matrix binding. Reason: As for the IBA row. Supporting Evidence: PMID:14769788 in its native form, DMP1 inhibits mineralization, but when cleaved or dephosphorylated, it initiates mineralization |
| GO:0140149 non-collagenous component of interstitial matrix | IDA PMID:36399478 MatrisomeDB 2.0: 2023 updates to the ECM-protein knowledge d... | ACCEPT | Summary: MatrisomeDB classifies DMP1 among non-collagenous matrix components. Reason: DMP1 is a non-collagenous matrix protein of bone and dentin; consistent with all other localization evidence. Supporting Evidence: PMID:12615915 This phosphorylated DMP1 is then exported out into the extracellular matrix, where it regulates nucleation of hydroxyapatite |
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Download this section (compressed HTML)Q: By what molecular mechanism does DMP1 loss increase osteocytic FGF23 expression: a cell-autonomous signal from matrix-bound DMP1 (e.g. via alphaVbeta3 integrin), an effect of impaired osteocyte maturation, or altered local phosphate sensing?
Q: Does DMP1 have a physiological nuclear transcriptional function in pre-osteoblasts in vivo, independent of its secreted matrix role?
Q: Is GO:0046848 hydroxyapatite binding a more accurate core molecular function than calcium ion binding for DMP1 and its C-terminal fragment?
Experiment: Osteocyte-specific rescue of Dmp1-null mice with secretion-competent versus nucleus-targeted or RGD-mutant DMP1, measuring Fgf23 expression, serum phosphate and mineralization, to separate the matrix, integrin and nuclear contributions.
Type: in vivo structure-function rescue
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