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Results for “ADAM12 Protein”

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PubMed2006

ADAM12-s in coelomic fluid and maternal serum in early pregnancy.

OBJECTIVES: ADAM12-s is a placental protein. In early pregnancy, reduced maternal levels of ADAM12-s have been reported in association with foetal trisomy 21 or 18 and in cases that subsequently develop pre-eclampsia and foetal growth restriction. The aim of this study is to investigate the distribution of ADAM12-s in early pregnancy by comparing its concentration in maternal serum, amniotic fluid and coelomic fluid. METHODS: Coelomic fluid was obtained by coelocentesis from 13 singleton pregnancies with live foetuses at 6.9-9.3 weeks of gestation. Maternal serum was also obtained in all cases and in six cases amniotic fluid was also obtained. The concentration of ADAM12-s was measured by dissociation enhanced lanthanide fluoro-immunoassay. RESULTS: The median concentration of ADAM12-s in maternal serum was 132.7 (range 33.8-254.5) ng/mL and in coelomic fluid it was 10.5 (range 1.3-15.8) ng/mL; there were no detectable levels in five of the six amniotic fluid samples. The concentration of maternal serum ADAM12-s increased significantly with gestation (r = 0.862, p < 0.0001). There was no significant association between coelomic fluid ADAM12-s and either gestation (r = 0.255, p = 0.401) or maternal serum ADAM12-s (r = 0.302, p = 0.316). CONCLUSION: The distribution of ADAM12-s in maternal serum and the early embryonic fluid compartments is consistent with its syncytiotrophoblastic origin.

ADAM Proteins↗

PubMed2006

Molecular profiling of ADAM12 in human bladder cancer.

PURPOSE: We have previously found ADAM12, a disintegrin and metalloprotease, to be an interesting biomarker for breast cancer. The purpose of this study was to determine the gene and protein expression profiles of ADAM12 in different grades and stages of bladder cancer. EXPERIMENTAL DESIGN: ADAM12 gene expression was evaluated in tumors from 96 patients with bladder cancer using a customized Affymetrix GeneChip. Gene expression in bladder cancer was validated using reverse transcription-PCR, quantitative PCR, and in situ hybridization. Protein expression was evaluated by immunohistochemical staining on tissue arrays of bladder cancers. The presence and relative amount of ADAM12 in the urine of cancer patients were determined by Western blotting and densitometric measurements, respectively. RESULTS: ADAM12 mRNA expression was significantly up-regulated in bladder cancer, as determined by microarray analysis, and the level of ADAM12 mRNA correlated with disease stage. Reverse transcription-PCR, quantitative PCR, and in situ hybridization validated the gene expression results. Using immunohistochemistry, we found ADAM12 protein expression correlated with tumor stage and grade. Finally, ADAM12 could be detected in the urine by Western blotting; ADAM12 was present in higher levels in the urine from patients with bladder cancer compared with urine from healthy individuals. Significantly, following removal of tumor by surgery, in most bladder cancer cases examined, the level of ADAM12 in the urine decreased and, upon recurrence of tumor, increased. CONCLUSIONS: ADAM12 is a promising biomarker of bladder cancer.

ADAM Proteins↗

PubMed2000

Binding of ADAM12, a marker of skeletal muscle regeneration, to the muscle-specific actin-binding protein, alpha -actinin-2, is required for myoblast fusion.

ADAM12 belongs to the transmembrane metalloprotease ADAM ("a disintegrin and metalloprotease") family. ADAM12 has been implicated in muscle cell differentiation and fusion, but its precise function remains unknown. Here, we show that ADAM12 is dramatically up-regulated in regenerated, newly formed fibers in vivo. In C2C12 cells, ADAM12 is expressed at low levels in undifferentiated myoblasts and is transiently up-regulated at the onset of differentiation when myoblasts fuse into multinucleated myotubes, whereas other ADAMs, such as ADAMs 9, 10, 15, 17, and 19, are expressed at all stages of differentiation. Using the yeast two-hybrid screen, we found that the muscle-specific alpha-actinin-2 strongly binds to the cytoplasmic tail of ADAM12. In vitro binding assays with GST fusion proteins confirmed the specific interaction. The major binding site for alpha-actinin-2 was mapped to a short sequence in the membrane-proximal region of ADAM12 cytoplasmic tail; a second binding site was identified in the membrane-distal region. Co-immunoprecipitation experiments confirm the in vivo association of ADAM12 cytoplasmic domain with alpha-actinin-2. Overexpression of the entire cytosolic ADAM12 tail acted in a dominant negative fashion by inhibiting fusion of C2C12 cells, whereas expression of a cytosolic ADAM12 lacking the major alpha-actinin-2 binding site had no effect on cell fusion. Our results suggest that interaction of ADAM12 with alpha-actinin-2 is important for ADAM12 function.

ADAM Proteins↗

PubMed2003

PACSIN3 binds ADAM12/meltrin alpha and up-regulates ectodomain shedding of heparin-binding epidermal growth factor-like growth factor.

A disintegrin and metalloprotease 12 (ADAM12/meltrin alpha) is a key enzyme implicated in the ectodomain shedding of membrane-anchored heparin-binding epidermal growth factor (EGF)-like growth factor (proHB-EGF)-dependent epidermal growth factor receptor (EGFR) transactivation. However, the activation mechanisms of ADAM12 are obscure. To determine how ADAM12 is activated, we screened proteins that bind to the cytoplasmic domain of ADAM12 using a yeast two-hybrid system and identified a protein called PACSIN3 that contains a Src homology 3 domain. An analysis of interactions between ADAM12 and PACSIN3 using glutathione S-transferase fusion protein revealed that a proline-rich region (amino acid residues 829-840) of ADAM12 was required to bind PACSIN3. Furthermore, co-immunoprecipitation and co-localization analyses of ADAM12 and PACSIN3 proteins also revealed their interaction in mammalian cells expressing both of them. The overexpression of PACSIN3 in HT1080 cells enhanced 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced proHB-EGF shedding. Furthermore, knockdown of endogenous PACSIN3 by small interfering RNA in HT1080 cells significantly attenuated the shedding of proHB-EGF induced by TPA and angiotensin II. Our data indicate that PACSIN3 has a novel function as an up-regulator in the signaling of proHB-EGF shedding induced by TPA and angiotensin II.

ADAM Proteins↗

PubMed2003

[Membrane-anchored heparin-binding EGF-like growth factor processing by ADAM12 in cardiac hypertrophy].

G-protein coupled receptor(GPCR) agonists are well-known inducers of cardiac hypertrophy. We found that the shedding of HB-EGF via metalloproteinase activation and subsequent transactivation of the epidermal growth factor receptor occurred when cardiomyocytes were stimulated by GPCR agonists, leading to cardiac hypertrophy. A new inhibitor of HB-EGF shedding, KB-R7785, blocked this signaling. We cloned a disintegrin and metalloprotease 12(ADAM12) as a specific enzyme to shed HB-EGF in the heart and found that dominant negative expression of ADAM12 abrogated this signaling. KB-R7785 bound directly to ADAM12, suggesting that inhibition of ADAM12 blocked the shedding of HB-EGF. In mice with cardiac hypertrophy, KB-R7785 inhibited the shedding of HB-EGF and attenuated hypertrophic changes. These data suggest that shedding of HB-EGF by ADAM12 plays an important role in cardiac hypertrophy, and that inhibition of HB-EGF shedding could be a potent therapeutic strategy for cardiac hypertrophy.

ADAM Proteins↗

PubMed2004

ADAM binding protein Eve-1 is required for ectodomain shedding of epidermal growth factor receptor ligands.

A disintegrin and metalloproteases (ADAMs) are implicated in the ectodomain shedding of epidermal growth factor receptor (EGFR) ligands in EGFR transactivation. However, the activation mechanisms of ADAMs remain elusive. To analyze the regulatory mechanisms of ADAM activation, we performed yeast two-hybrid screening using the cytoplasmic domain of ADAM12 as bait, and identified a protein that we designated Eve-1. Two cDNAs were cloned and characterized. They encode alternatively spliced isoforms of Eve-1, called Eve-1a and Eve-1b, that have four and five tandem Src homology 3 (SH3) domains in the carboxyl-terminal region, respectively, and seven proline-rich SH3 domain binding motifs in the amino-terminal region. The short forms of Eve-1, Eve-1c and Eve-1d, translated at Met-371 are human counterparts of mouse Sh3d19. Northern blot analysis demonstrated that Eve-1 is abundantly expressed in skeletal muscle and heart. Western blot analysis revealed the dominant production of Eve-1c in human cancer cell lines. Knockdown of Eve-1 by small interfering RNA in HT1080 cells reduced the shedding of proHB-EGF induced by angiotensin II and 12-O-tetradecanoylphorbol-13-acetate, as well as the shedding of pro-transforming growth factor-alpha, promphiregulin, and proepiregulin by 12-O-tetradecanoylphorbol-13-acetate, suggesting that Eve-1 plays a role in positively regulating the activity of ADAMs in the signaling of EGFR-ligand shedding.

ADAM Proteins↗

PubMed2006

ADAM19 is tightly associated with constitutive Alzheimer's disease APP alpha-secretase in A172 cells.

To elucidate whether new proteases are involved in the processing of amyloid precursor protein (APP), we examined catalytically active ADAM12 and ADAM19 as candidates alpha-secretases. The overexpression of ADAM19 in HEK293 cells resulted in an increase in sAPPalpha. Therefore, we suggest that ADAM19 has a constitutive alpha-secretase activity. We examined regulated alpha-secretase activity by adding phorbol 12-myristate 13-acetate (PMA), but no regulated activity was found. To verify that endogenous ADAM19 has an APP alpha-secretase activity, we examined whether the constitutive level of alpha-secretase activity was reduced by RNA interference with ADAM19 in A172 cells. The amount of secreted sAPPalpha decreased by about 21% following RNAi. These results suggest that ADAM19 has a constitutive alpha-secretase activity for APP.

ADAM Proteins↗

PubMed1998

Spatially- and temporally-restricted expression of meltrin alpha (ADAM12) and beta (ADAM19) in mouse embryo.

The cloning of the full-length cDNA encoding meltrin beta (ADAM19), one of the metalloprotease-disintegrins expressed in mouse myogenic cells, revealed that the meltrin beta gene encodes a membrane protein closely related to meltrin alpha (ADAM12) which participates in myotube formation in vitro. To delineate the functions of meltrin alpha and beta, we examined the expression patterns of their transcripts during embryogenesis. The meltrin alpha gene is activated in condensed mesenchymal cells that give rise to skeletal muscle, bones and visceral organs. Meltrin beta mRNA, in contrast, is markedly expressed in craniofacial and dorsal root ganglia and ventral horns of the spinal cord, where peripheral neuronal cell lineages differentiate. Heart, skeletal muscle, intestine and lung also express meltrin beta mRNA transiently. Although the meltrin alpha and beta transcripts exhibit distinct expression patterns during embryogenesis, both genes are mainly activated in mesenchymal cells that are derived from both mesoderm and ectoderm.

ADAM Proteins↗

PubMed2002

ADAM12/syndecan-4 signaling promotes beta 1 integrin-dependent cell spreading through protein kinase Calpha and RhoA.

The ADAMs (a disintegrin and metalloprotease) comprise a large family of multidomain proteins with cell-binding and metalloprotease activities. The ADAM12 cysteine-rich domain (rADAM12-cys) supports cell attachment using syndecan-4 as a primary cell surface receptor that subsequently triggers beta(1) integrin-dependent cell spreading, stress fiber assembly, and focal adhesion formation. This process contrasts with cell adhesion on fibronectin, which is integrin-initiated but syndecan-4-dependent. In the present study, we investigated ADAM12/syndecan-4 signaling leading to cell spreading and stress fiber formation. We demonstrate that syndecan-4, when present in significant amounts, promotes beta(1) integrin-dependent cell spreading and stress fiber formation in response to rADAM12-cys. A mutant form of syndecan-4 deficient in protein kinase C (PKC)alpha activation or a different member of the syndecan family, syndecan-2, was unable to promote cell spreading. GF109203X and Gö6976, inhibitors of PKC, completely inhibited ADAM12/syndecan-4-induced cell spreading. Expression of syndecan-4, but not syn4DeltaI, resulted in the accumulation of activated beta(1) integrins at the cell periphery in Chinese hamster ovary beta1 cells as revealed by 12G10 staining. Further, expression of myristoylated, constitutively active PKCalpha resulted in beta(1) integrin-dependent cell spreading, but additional activation of RhoA was required to induce stress fiber formation. In summary, these data provide novel insights into syndecan-4 signaling. Syndecan-4 can promote cell spreading in a beta(1) integrin-dependent fashion through PKCalpha and RhoA, and PKCalpha and RhoA likely function in separate pathways.

ADAM Proteins↗

PubMed2005

RhoA GTPase regulates M-cadherin activity and myoblast fusion.

The Rho family of GTP-binding proteins plays critical roles during myogenesis induction. To elucidate their role later during myogenesis, we have analyzed RhoA function during myoblast fusion into myotubes. We find that RhoA activity is rapidly and transiently increased when cells are shifted into differentiation medium and then is decreased until myoblast fusion. RhoA activity must be down-regulated to allow fusion, because expression of a constitutively active form of RhoA (RhoAV14) inhibits this process. RhoAV14 perturbs the expression and localization of M-cadherin, a member of the Ca2+-dependent cell-cell adhesion molecule family that has an essential role in skeletal muscle cell differentiation. This mutant does not affect N-cadherin and other proteins involved in myoblast fusion, beta1-integrin and ADAM12. Active RhoA induces the entry of M-cadherin into a degradative pathway and thus decreases its stability in correlation with the monoubiquitination of M-cadherin. Moreover, p120 catenin association with M-cadherin is decreased in RhoAV14-expressing cells, which is partially reverted by the inhibition of the RhoA effector Rho-associated kinase ROCK. ROCK inhibition also restores M-cadherin accumulation at the cell-cell contact sites. We propose that the sustained activation of the RhoA pathway inhibits myoblast fusion through the regulation of p120 activity, which controls cadherin internalization and degradation.

ADAM Proteins↗

PubMed2003

ADAM12 in human liver cancers: TGF-beta-regulated expression in stellate cells is associated with matrix remodeling.

"A disintegrin and metalloproteinases" (ADAMs) form a family of cell-surface glycoproteins with potential protease and cell-adhesion activities. We have investigated ADAM expression in human liver cancers and their regulation by several cytokines involved in liver injury. Using degenerative RT-PCR, cDNA encoding sequences for ADAM9 and ADAM12 were identified in human activated hepatic stellate cells (HSCs). Northern blot analyses showed that HSCs, but not hepatocytes, expressed transcripts for ADAM9 messenger RNA (mRNA) and both the long and short forms of ADAM12. This expression was associated with the transition from quiescent to activated state of rat HSCs and markedly increased in human livers with cirrhosis. ADAM12 but not ADAM9 expression was up-regulated by transforming growth factor beta (TGF-beta) in human activated HSCs. The PI3K inhibitor LY294002 and the mitogen-activated protein kinase kinase (MEK) inhibitor UO126 prevented ADAM12 induction by TGF-beta, suggesting the involvement of PI3K and MEK activities. In vivo, the steady-state of both ADAM9 and ADAM12 mRNA levels was nearly undetectable in both normal livers and benign tumors and increased in hepatocellular carcinomas (up to 3- and 6-fold, respectively) and liver metastases from colonic carcinomas (up to 40- and 60-fold, respectively). The up-regulation of both ADAM9 and ADAM12 was correlated with an increase in matrix metalloproteinase 2 expression and activity. In conclusion, in liver cancers ADAM9 and ADAM12 expression is associated with tumor aggressiveness and progression.

ADAM Proteins↗

PubMed2005

Involvement of the serine/threonine p70S6 kinase in TGF-beta1-induced ADAM12 expression in cultured human hepatic stellate cells.

BACKGROUND/AIMS: In chronic liver injury, quiescent hepatic stellate cells change into proliferative myofibroblast-like cells, which are a main source of fibrosis. We have recently reported that these cells synthesize ADAM12, a disintegrin and metalloprotease whose expression is up-regulated by TGF-beta1 in liver cancers. Here, we studied the role of the serine/threonine p70S6 kinase (p70S6K) in regulating TGF-beta1-induced ADAM12 expression. RESULTS: The phophatidylinositol 3-kinase (PI3K) inhibitor LY294002 and the mitogen-activated protein kinase inhibitor, UO126, decreased the TGF-beta1-dependent ADAM12 expression and prevented the phosphorylation of p70S6K. In addition, TGF-beta1-induced ADAM12 up-regulation was blocked by the Frap/mTOR inhibitor rapamycin, which abrogated the phosphorylation of p70S6K. In untreated cells, LY294002 but not rapamycin diminished the basal ADAM12 expression related to inhibition of Akt and the glycogen synthase kinase-3 phosphorylation. CONCLUSIONS: The data suggest that TGF-beta1 induces ADAM12 gene expression through both the PI3K/Frap-mTOR/p70S6K and MEK/ERK pathways. In addition, activation of the PI3 pathway might be involved in the basal ADAM12 expression in cultured hepatic stellate cells. The involvement of PI3K in ADAM12 expression, similar to that previously observed for collagen I and fibronectin, suggests common pathways for gene up-regulation in hepatic stellate cells that occur during liver fibrogenesis and contribute to tumor progression.

ADAM Proteins↗

PubMed2006

ADAM12 is a four-leafed clover: the excised prodomain remains bound to the mature enzyme.

The ADAMs (a disintegrin and metalloprotease) comprise a family of multidomain proteins with metalloprotease, cell adhesion, and signaling activities. Human ADAM12, which is implicated in diseases such as cancer, is expressed in two splice forms, the transmembrane ADAM12-L and the shorter and soluble ADAM12-S. ADAM12 is synthesized as a zymogen with the prodomain keeping the metalloprotease inactive through a cysteine-switch mechanism. Maturation and activation of the protease involves the cleavage of the prodomain in the trans-Golgi or possibly at the cell surface by a furin-peptidase. The aim of the present study was to determine the fate of the prodomain following furin cleavage. Here we demonstrate that, following cleavage of the human ADAM12-S prodomain in the trans-Golgi by a furin-peptidase, the prodomain remains non-covalently associated with the mature molecule. Accordingly, both the 68-kDa mature form of ADAM12-S and the 25-kDa prodomain could be detected using domain-specific antisera in immunoprecipitation and Western blot analyses of human serum ADAM12 and purified recombinant human ADAM12. Using electron microscopy after negative staining we have furthermore obtained the first visualization of a full-length ADAM molecule, human ADAM12-S, and report that it appears to be a compact clover composed of four globular domains, one of which is the prodomain. Finally, our data demonstrate that the presence of the metalloprotease domain appears to be sufficient for the prodomain to remain associated with the mature ADAM12-S. Thus, we conclude that the prodomain of human ADAM12-S is an integral domain of the mature molecule and as such might have specific biological functions in the extracellular space.

ADAM Proteins↗

PubMed2005

Hierarchy of ADAM12 binding to integrins in tumor cells.

ADAMs (a disintegrin and metalloprotease) comprise a family of cell surface proteins with protease and cell-binding activities. Using different forms and fragments of ADAM12 as substrates in cell adhesion and spreading assays, we demonstrated that alpha9beta1 integrin is the main receptor for ADAM12. However, when alpha9beta1 integrin is not expressed--as in many carcinoma cells--other members of the beta1 integrin family can replace its ligand binding activity. In attachment assays, the recombinant disintegrin domain of ADAM12 only supported alpha9 integrin-dependent tumor cell attachment, whereas full-length ADAM12 supported attachment via alpha9 integrin and other integrin receptors. Cells that attached to full-length ADAM12 in an alpha9 integrin-dependent manner also attached to ADAM12 in which the putative alpha9beta1 integrin-binding motif in the disintegrin domain had been mutated. This attachment was mediated through use of an alternate beta1 integrin. We also found that cell spreading in response to ADAM12 is dependent on the apparent level of integrin activation. Binding of cells to ADAM12 via the alpha9beta1 integrin was Mn(2+)-independent and resulted in attachment of cells with a rounded morphology; attachment of cells with a spread morphology required further activation of the alpha9beta1 integrin. We demonstrated that phosphoinositide-3-kinase appears to be central in regulating alpha9beta1 integrin cell spreading activity in response to ADAM12.

ADAM Proteins↗

PubMed2005

[Expression of macrophage inflammatory protein-1alpha, a disintegrin-like and metalloproteinase 8 and 12, and CD68 protein in giant cell lesions of jaw and giant cell tumors of long bone].

OBJECTIVE: To detect the expression of macrophage inflammatory protein-1alpha (MIP-1alpha), a disintegrin-like and metalloproteinase (ADAM) 8 and 12 and CD68 protein in giant cell lesions of jaw and giant cell tumors of long bone, and to study their effects on the histogenesis of giant cells in such lesions. METHODS: MIP-1alpha, ADAM8, ADAM12 and CD68 were detected by immunohistochemistry in 24 paraffin-embedded specimens of central giant cell lesions of jaw and giant cell tumors respectively. RESULTS: MIP-1alpha positive signal was located in blood vessels and bone. ADAM8, ADAM12 and CD68 positive signals were located in the cell membrane and cytoplasm of all multinucleated giant cells and some round mononuclear cells in the lesions. In addition, some spindle mononuclear stromal cells were positive for ADAM12 in both lesions. CONCLUSION: Multinucleated giant cells probably originate from CD68-postive round mononuclear cells, which are recruited from monocyte-macrophage system by chemokines, such as MIP-1alpha, followed by cell fusion mediated by ADAM8 and ADAM12.

ADAM Proteins↗

PubMed2004

[Expression of a disintegrin-like and metalloproteinase protein 8 and 12 in the giant cell lesions of jaw].

OBJECTIVE: To detect the expression of a disintegrin-like and metalloproteinase (ADAM) 8 and 12 gene in the giant cell lesions of jaw and to study their effects on the histogenesis of cells in these lesions. METHODS: ADAM8 and ADAM12 was detected by immunohistochemistry (SP) in 40 paraffin-embedded specimens of central giant cell lesions of jaw, 10 peripheral giant cell lesions, 9 cherubisms, 6 aneurysmal bone cysts. RESULTS: ADAM8 and ADAM12 were positive in the cytomembrane and cytoplasm of all multinucleated giant cells and some round mononuclear cells of the lesions; ADAM12 was positive for some spindle mononuclear stromal cells in central and peripheral giant cell lesions. CONCLUSIONS: Multinucleated giant cells probably originated from the fusion of the round mononuclear cells, and ADAM8 and ADAM12 were involved in this process. In addition, ADAM12 might play a role in the maturation of spindle mononuclear stromal cells.

ADAM Proteins↗

PubMed2002

Intracellular processing of metalloprotease disintegrin ADAM12.

ADAM12 has been implicated in cell-cell interactions in myogenesis and cancer, but the structure of the mature form of ADAM12 is not known, and its localization on the cell surface has been questioned. In this report, we show that full-length ADAM12 is N-glycosylated in the endoplasmic reticulum (ER) and proteolytically processed in the trans-Golgi network to an approximately 90-kDa form. The approximately 90-kDa form, which lacks the prodomain, was the predominant form present at the cell surface. Replacement of Leu(73) in the putative alpha-helical region in the prodomain with proline resulted in retention of ADAM12 in the ER and a complete lack of its processing. However, deletion of the entire pro- and metalloprotease domains did not affect the processing and trafficking of ADAM12. In contrast, replacement of the cytoplasmic domain of ADAM12 with that of ADAM9 or adding a c-Myc tag at the C terminus led to a significant increase in transport of the protein to the cell surface. These results suggest that the cytoplasmic domain of ADAM12 plays an important role in regulating ADAM12 exit from the ER. We conclude that properly folded mouse ADAM12, after passing a rate-limiting step of exit from the ER, is processed in the secretory pathway and reaches the cell surface, where it can mediate adhesion-mediated signaling.

ADAM Proteins↗

PubMed2006

Proteolytic processing of delta-like 1 by ADAM proteases.

Delta-like 1 (Dll1) is a mammalian ligand for Notch receptors. Interactions between Dll1 and Notch in trans activate the Notch pathway, whereas Dll1 binding to Notch in cis inhibits Notch signaling. Dll1 undergoes proteolytic processing in its extracellular domain by ADAM10. In this work we demonstrate that Dll1 represents a substrate for several other members of the ADAM family. In co-transfected cells, Dll1 is constitutively cleaved by ADAM12, and the N-terminal fragment of Dll1 is released to medium. ADAM12-mediated cleavage of Dll1 is cell density-dependent, takes place in cis orientation, and does not require the presence of the cytoplasmic domain of ADAM12. Full-length Dll1, but not its N- or C-terminal proteolytic fragment, co-immunoprecipitates with ADAM12. By using a Notch reporter construct, we show that Dll1 processing by ADAM12 increases Notch signaling in a cell-autonomous manner. Furthermore, ADAM9 and ADAM17 have the ability to process Dll1. In contrast, ADAM15 does not cleave Dll1, although the two proteins still co-immunoprecipitate with each other. Asn-353 present in the catalytic motif of ADAM12 and other Dll1-processing ADAMs, but absent in ADAM15, is necessary for Dll1 cleavage. Dll1 cleavage is reduced in ADAM9/12/15(-/-) mouse embryonic fibroblasts (MEFs), suggesting that the endogenous ADAM9 and/or ADAM12 present in wild type MEFs contribute to Dll1 processing. Finally, the endogenous Dll1 present in primary mouse myoblasts undergoes cleavage in confluent, differentiating myoblast cultures, and this cleavage is decreased by ADAM12 small interfering RNAs. Our findings expand the role of ADAM proteins in the regulation of Notch signaling.

ADAM Proteins↗