Native and Activated Forms of α2-Macroglobulin Increase Expression of Platelet-derived Growth Factor α-Receptor in Vascular Smooth Muscle Cells

Weaver, Alissa M.; Owens, Gary K.; Gonias, Steven L.

doi:10.1074/jbc.270.51.30741

Cited by 27 publications

(20 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The TGF-␤-binding site was located in the center of the ␣ 2 M subunit (aa 591-774) and overlapped with the bait domain. Binding of TGF-␤ to ␣ 2 M may be particularly important since ␣ 2 M regulates the activity of TGF-␤ that is produced endogenously by cells in culture (22)(23)(24). Furthermore, the ␣ 2 M gene knock-out mouse demonstrates abnormal responses to various forms of exogenous challenge that may be attributed to deficient TGF-␤ regulation (25,26).…”

mentioning

confidence: 99%

Identical or Overlapping Sequences in the Primary Structure of Human α2-Macroglobulin Are Responsible for the Binding of Nerve Growth Factor-β, Platelet-derived Growth Factor-BB, and Transforming Growth Factor-β

Gonias¹,

Carmichael²,

Mettenburg³

et al. 2000

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

mentioning

confidence: 99%

Identical or Overlapping Sequences in the Primary Structure of Human α2-Macroglobulin Are Responsible for the Binding of Nerve Growth Factor-β, Platelet-derived Growth Factor-BB, and Transforming Growth Factor-β

Gonias¹,

Carmichael²,

Mettenburg³

et al. 2000

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

“…In cell culture systems, ␣ 2 M neutralizes both exogenously added and endogenously synthesized TGF-␤ (24 -28). Neutralization of endogenously synthesized TGF-␤ results in altered gene expression, including greatly increased expression of inducible nitric-oxide synthase by murine macrophages and increased expression of plateletderived growth factor ␣-receptor by vascular smooth muscle cells (27,28). ␣ 2 M gene knockout mice demonstrate increased tolerance to endotoxin challenge (29); this characteristic is most likely explained by the enhanced function of TGF-␤ as an immunosuppressant, in the absence of ␣ 2 M (30).…”

mentioning

confidence: 99%

Localization of the Binding Site for Transforming Growth Factor-β in Human α2-Macroglobulin to a 20-kDa Peptide That Also Contains the Bait Region

Webb¹,

Wen²,

Karns³

et al. 1998

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

and TGF-␤2 in fetal bovine heart endothelial (FBHE) cell proliferation assays; FP4 was inactive in this assay. FP3 also increased NO synthesis by RAW 264.7 cells, mimicking an ␣ 2 M activity that has been attributed to the neutralization of endogenously synthesized TGF-␤. Thus, we have isolated a peptide corresponding to 13% of the ␣ 2 M sequence that binds TGF-␤ and neutralizes the activity of TGF-␤ in two separate biological assays.1 is a 718-kDa glycoprotein that was originally characterized as a broad spectrum proteinase inhibitor (1). The structure of ␣ 2 M consists of four identical subunits, each with 1451 amino acids (2). The subunits are linked into dimers by disulfide bonds and into intact homotetramers by noncovalent interactions (3, 4). Proteinases react with ␣ 2 M by cleaving any of a number of susceptible peptide bonds in the "bait region," which includes amino acids 666 -706 (1, 3, 5). Bait region cleavage causes ␣ 2 M to undergo a major conformational change, which effectively "traps" the attacking proteinase in a complex that is nondissociable, even when the proteinase and the inhibitor are not covalently linked (1, 6 -8).Conformational change also reveals binding sites for the ␣ 2 M receptor/low density lipoprotein receptor-related protein (LRP) (9). These binding sites have been localized to 18-kDa peptides at the C terminus of each ␣ 2 M subunit; Lys-1370 and Lys-1374 play particularly important roles (10 -13).Like the complement components, C3 and C4, each ␣ 2 M subunit contains a novel thiol ester bond, which is formed from the side chains of . The thiol esters may be instrumental in determining the conformational state of ␣ 2 M (17, 18). When ␣ 2 M reacts with a proteinase, the thiol esters emerge from within hydrophobic, solvent-restricted clefts and are cleaved by nucleophiles or H 2 O (14, 18). Small primary amines, such as methylamine, penetrate the hydrophobic clefts and react with ␣ 2 M thiol esters independently of proteinases, inducing an equivalent or nearly equivalent conformational change (6, 7).In addition to its activity as a proteinase inhibitor, ␣ 2 M functions as a major carrier and regulator of certain cytokines, including isoforms of the transforming growth factor-␤ (TGF-␤) family. O'Connor-McCourt and Wakefield (19) first identified ␣ 2 M as a physiologically significant carrier of TGF-␤ in human serum (19). Their studies demonstrated that nearly all of the TGF-␤1 in serum is associated with ␣ 2 M and that the bound TGF-␤1 is inactive. Huang et al. (20) More recent studies have demonstrated the function of ␣ 2 M as a TGF-␤-carrier in animal model systems. When radioiodinated TGF-␤1 is injected intravascularly in mice, the cytokine is cleared rapidly at first; however, this is followed by a slow clearance phase, during which time the TGF-␤ is almost entirely ␣ 2 M-associated (21-23). In cell culture systems, ␣ 2 M neutralizes both exogenously added and endogenously synthesized TGF-␤ (24 -28). Neutralization of endogenously synthesized TGF-␤ results in altered gene expr...

show abstract

“…␣ 2 M-carrier interactions are principally reversible in nature (7). As a result, ␣ 2 M may inhibit growth factor activity (9,10) or stabilize the growth factor for potential delivery to cell signaling receptors (11). There also is evidence that ␣ 2 M, which is "activated" by reaction with proteases, initiates cell signaling by binding to LRP-1 (12)(13)(14)(15) or other receptors, such as glucose-regulated protein-78 (Grp 78) (16,17).…”

mentioning

confidence: 99%

Molecular Dissection of the Human α2-Macroglobulin Subunit Reveals Domains with Antagonistic Activities in Cell Signaling

Mantuano

Mukandala

et al. 2008

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

␣ 2 -Macroglobulin (␣ 2 M) is a plasma protease inhibitor, which reversibly binds growth factors and, in its activated form, binds to low density lipoprotein receptor-related protein (LRP-1), an endocytic receptor with cell signaling activity. Because distinct domains in ␣ 2 M are responsible for its various functions, we hypothesized that the overall effects of ␣ 2 M on cell physiology reflect the integrated activities of multiple domains, some of which may be antagonistic. To test this hypothesis, we expressed the growth factor carrier site and the LRP-1 recognition domain (RBD) as separate GST fusion proteins (FP3 and FP6, respectively). 2 is a 718-kDa homotetrameric glycoprotein, found in the plasma and extracellular spaces, which was first recognized as a broad spectrum protease inhibitor (1). Reaction with proteases induces a major conformational change in ␣ 2 M so that the protease is physically trapped (2, 3). The same conformational change reveals a cryptic recognition site for low density lipoprotein receptor-related protein (LRP-1) (4, 5). Because of the function of LRP-1 as an endocytic receptor, ␣ 2 M-protease complexes are rapidly cleared from the bloodstream and probably other sites of generation (6).In addition to its role as a protease inhibitor, ␣ 2 M is an important carrier of specific growth factors, including transforming growth factor-␤ (TGF-␤), platelet-derived growth factor-BB (PDGF-BB), nerve growth factor-␤ (NGF-␤), and neurotrophin-4 (7, 8). ␣ 2 M-carrier interactions are principally reversible in nature (7). As a result, ␣ 2 M may inhibit growth factor activity (9, 10) or stabilize the growth factor for potential delivery to cell signaling receptors (11). There also is evidence that ␣ 2 M, which is "activated" by reaction with proteases, initiates cell signaling by binding to LRP-1 (12-15) or other receptors, such as glucose-regulated protein-78 (Grp 78) (16,17). However, in studies with intact ␣ 2 M, the possibility that cell signaling results from growth factors that are carried by ␣ 2 M must be considered (11,18).A structural model of ␣ 2 M has been developed, based on the crystal structure of complement component C3, which is homologous to ␣ 2 M (19). This model describes ␣ 2 M as a modular structure, consisting of multiple independently folded domains. To localize ␣ 2 M domains that are responsible for various activities, our laboratory generated a library of glutathione S-transferase (GST) fusion proteins, containing overlapping segments of the ␣ 2 M subunit (20 -22). Fusion protein-3 (FP3) includes residues 591-774 and contains the sequence in ␣ 2 M responsible for binding growth factors. FP6 contains amino acids 1242-1451 and the LRP-1-binding site, in which a single ␣-helix that includes Lys 1370 and Lys 1374 plays a central role (23,24). Assignment of ␣ 2 M activities to specific fusion proteins, such as FP3 and FP6, has been validated by mutagenesis of full-length recombinant ␣ 2 M (25, 26). Thus, the ␣ 2 M fusion proteins provide an opportunity to assess activities assigne...

show abstract

Native and Activated Forms of α2-Macroglobulin Increase Expression of Platelet-derived Growth Factor α-Receptor in Vascular Smooth Muscle Cells

Cited by 27 publications

References 58 publications

Identical or Overlapping Sequences in the Primary Structure of Human α2-Macroglobulin Are Responsible for the Binding of Nerve Growth Factor-β, Platelet-derived Growth Factor-BB, and Transforming Growth Factor-β

Identical or Overlapping Sequences in the Primary Structure of Human α2-Macroglobulin Are Responsible for the Binding of Nerve Growth Factor-β, Platelet-derived Growth Factor-BB, and Transforming Growth Factor-β

Localization of the Binding Site for Transforming Growth Factor-β in Human α2-Macroglobulin to a 20-kDa Peptide That Also Contains the Bait Region

Molecular Dissection of the Human α2-Macroglobulin Subunit Reveals Domains with Antagonistic Activities in Cell Signaling

Contact Info

Product

Resources

About