Details

Autor(en) / Beteiligte

• Schober, Joseph M

Titel

CCN protein expression in atherosclerotic lesions and interaction with integrin receptors on monocytes

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2003

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• CCN1 and CCN2 are growth factor-inducible immediate-early gene products found in blood vessel walls and healing cutaneous wounds. Both CCN proteins have been shown to support cell adhesion and induce cell migration through interaction with integrin receptors. In this study, we demonstrated that both CCN1 and CCN2 are expressed in atherosclerotic lesions of apolipoprotein E-deficient mice. Since monocytes are also present within atherosclerotic lesions, we examined the interaction of these cells with CCN1 and CCN2. Monocytes adhered to CCN1- or CCN2-coated wells in an activation-dependent manner and this process was mediated primarily through integrin αMβ2. Additionally, expression of αMβ2 in human embryonic kidney 293 cells resulted in enhanced cell adhesion to CCN1. Consistent with these data, a GST-fusion protein containing the I-domain of the integrin α M subunit (GST-αMI) bound specifically to immobilized CCN1 or CCN2. These results show that monocytes adhere to CCN1 and CCN2 through integrin αMβ2. To localize the α Mβ2 binding site in CCN1, we tested the ability of CCN1-derived peptides to support monocyte adhesion and GST-αMI binding. Monocytes adhered to a synthetic peptide derived from a conserved region within the CCN1 C-terminal domain (CCN1-H2-SSVKKYRPKYCGS), and this process was blocked an anti-αM monoclonal antibody. Consistently, the α MI-domain bound to immobilized CCN1-H2, peptide as well as to the corresponding CCN2-H2 sequence. By contrast, a scrambled CCN1-H2 peptide and an 18-residue peptide derived from a sequence adjacent to CCN1-H2 failed to support monocyte adhesion or αMI-domain binding. To confirm that the CCN1-H2 sequence within the CCN1 protein mediates αMβ2 interaction, we developed an anti-peptide antibody against CCN1-H2 and showed that it specifically blocked GST-αMI binding to intact CCN1. Collectively, these studies identify (1) integrin α Mβ2 as the major receptor on monocytes mediating cell adhesion to CCN1 and CCN2 and (2) the H2 sequence in CCN1 and CCN2 as a novel integrin αMβ2 binding motif, which bears no apparent homology to any αMβ2 binding sequence reported to date.