αvβ1 is a receptor for vitronectin and fibrinogen, and acts with α5β1 to mediate spreading on fibronectin

Abstract

We have shown previously that VUP was the only line out of ten human melanoma lines that failed to express the vitronectin receptor alpha v beta 3, but instead expressed alpha v beta 1. Levels of alpha v beta 1 expression were low on parental VUP cells so that iterative sorting by FACS, using an anti-alpha v antibody (13C2), was utilised to derive sublines with 8- to 10-fold higher amounts of cell surface alpha v beta 1. There was little difference between low (V-) and high (V+) alpha v beta 1-expressing sublines with regard to adherence to collagen type I, collagen type IV or laminin substrata. However, adherence to vitronectin and fibrinogen correlated closely with alpha v beta 1 expression (35-42% adhesion for V(+) lines versus 6–8% adhesion for V- lines on vitronectin, for example). Utilising a high alpha v beta 1-expressing subline (V + B2) we have shown that binding to vitronectin and fibrinogen was inhibited specifically by function-blocking antibodies to alpha v (17E6 and 14D9) and beta 1 (A11B2). V(+) sublines spread more compared with V(-) sublines on both vitronectin and fibronectin. However, neither alpha 5- nor alpha v-blocking antibodies had any effect on attachment or spreading of V + B2 on fibronectin whereas the combination of alpha 5 (PID6)- and alpha v(17E6)-blocking antibodies abrogated binding to fibronectin almost completely. This is the first report of an alpha v beta 1 integrin able to recognize vitronectin and fibrinogen, and also cooperate with alpha 5 beta 1 to mediate attachment to and spreading on fibronectin.

Chemiluminescent Measurement of Telomere DNA Content in Biopsies

“…Adherent cell lines were harvested and printed after a small period of trypsination. This procedure does not reduce the ability of antibodies to recognize MHC antigens (21). Cell microarrays were immunostained with MHC Ispecific (Figure 3, A-E) and MHC II-specific (Figure 3, F-J) antibodies, and signal intensities were calculated for each triplicate of microspots of the same cell line.…”

Fibrinogen inhibits sonic hedgehog signaling and impairs neonatal cerebellar development after blood–brain barrier disruption

“…Like SHH, fibrinogen binds HSPGs through a heparin-binding domain ( 49 , 50 ), so fibrinogen may compete with SHH for HSPG binding which would limit SHH bioavailability at the cell surface. Likewise, fibrinogen binds to beta1 integrins expressed in CGNPs ( 48 , 51 ), so fibrinogen–integrin interactions could impair the recruitment of SHH–laminin complexes to the surface of CGNPs and limit their proliferative response ( 48 ). Fibrinogen may also activate receptor signaling pathways that inhibit intracellular SHH signaling cascades in CGNPs.…”

Biphasic reinforcement of nascent adhesions by vinculin

“…Several β1-containing integrins, such as α5β1, α8β1, and ανβ1, mediate adhesion to FN, whereas integrins ανβ3, ανβ1, ανβ5, and α8β1 have been described as VN integrin receptors. 28,68 To verify that the measured adhesion forces are integrin-mediated, we performed force measurements either in the presence of an anti-β1 integrin antibody (clone Ha2/5) known to block β1 integrin-dependent adhesion to FN, or in the presence of RGD peptide to block integrin-mediated adhesion to VN. Both reagents efficiently reduced wt cell adhesion to the respective ECM protein (Figure S3), confirming that adhesion to FN and VN was primarily mediated by integrins.…”