Angiopoietin-Like 4 Interacts with Integrins β1 and β5 to Modulate Keratinocyte Migration

Abstract

Adipose tissue secretes adipocytokines for energy homeostasis, but recent evidence indicates that some adipocytokines also have a profound local impact on wound healing. Upon skin injury, keratinocytes use various signaling molecules to promote reepithelialization for efficient wound closure. In this study, we identify a novel function of adipocytokine angiopoietin-like 4 (ANGPTL4) in keratinocytes during wound healing through the control of both integrin-mediated signaling and internalization. Using two different in vivo models based on topical immuno-neutralization of ANGPTL4 as well as ablation of the ANGPTL4 gene, we show that ANGPTL4-deficient mice exhibit delayed wound reepithelialization with impaired keratinocyte migration. Human keratinocytes in which endogenous ANGPTL4 expression was suppressed by either siRNA or a neutralizing antibody show impaired migration associated with diminished integrin-mediated signaling. Importantly, we identify integrins ␤1 and ␤5, but not ␤3, as novel binding partners of AN-GPTL4. ANGPTL4-bound integrin ␤1 activated the FAKSrc-PAK1 signaling pathway, which is important for cell migration. The findings presented herein reveal an unpredicted role of ANGPTL4 during wound healing and demonstrate how ANGPTL4 stimulates intracellular signaling mechanisms to coordinate cellular behavior. Our findings provide insight into a novel cell migration control mechanism and underscore the physiological importance of the modulation of integrin activity in cancer metastasis.

Involvement of Angiopoietin-like 4 in Matrix Remodeling during Chondrogenic Differentiation of Mesenchymal Stem Cells

“…In addition, ANGPTL4 may have indirectly enhanced diffusional release of intact or MMP-cleaved aggrecan by disrupting the type II collagen network. The amount of soluble endogenous ANGPTL4 released by differentiating MSCs reached ϳ 94 nM, a value similar to or above reported affinities for integrin subunits ␤1 and ␤5 (24,25). Importantly, the total amount of ANGPTL4 produced by MSCs is likely to be even greater than that found in the supernatant alone because this protein was shown to be also retained in the extracellular matrix in a biologically active form bound to heparan sulfate proteoglycans, vitronectin, or fibronectin (28,29).…”

“…1D). Indeed, ANGPTL4 has been shown to bind integrins ␤1 and ␤5 with a K D of ϳ10 nM or 100 nM, depending on the study, and to modulate integrinmediated signaling (24,25). The use of recombinant ANGPTL4 at a concentration of 100 nM was thus expected to be appropriate to examine the role of this protein in the present study.…”

“…Blocking Antibody to Integrin ␣V␤5 Stimulates the Formation of Cartilaginous Matrix by Differentiating MSCs-Integrin ␣V␤5 is one of the transmembrane receptors for ANGPTL4 (24,25). Quantitative PCR showed that the genes encoding both chains forming this integrin, namely ITGAV and ITGB5, were expressed in undifferentiated MSCs (mean Ct ϭ 28.20 Ϯ 1.53 cycles and 26.83 Ϯ 1.07 cycles, respectively, compared with Ct ϭ 24.96 Ϯ 0.40 cycles for the housekeeping gene RPS9) and throughout TGF-␤-3-induced chondrogenesis in a relative constant manner (data not shown).…”

Fatty acid-inducible ANGPTL4 governs lipid metabolic response to exercise

“…After three washing steps with PBS, sections were incubated for 45 min at room temperature with the appropriate fluorescent-labeled secondary antibodies. The specificity of the antibody for ANGPTL4 was demonstrated previously via immunoblot of human plasma using appropriate peptide controls and was corroborated by immunochemical and immunofluorescence staining of ANGPTL4 in human heart, intestine, and skin wounds, using appropriate negative controls (15,47,48).…”

Emerging Roles of Angiopoietin-like 4 in Human Cancer

“…Matricellular proteins are a group of nonstructural, extracellular matrix (ECM)-associated glycoproteins secreted by cancer cells and neighboring stromal cells into the extracellular environment (4,5). This large group of structurally and functionally diverse proteins modulates cellmatrix interactions and cell functions by interacting with membrane receptors, proteases, hormones, and other bioeffector molecules, as well as with structural matrix proteins such as collagen and vitronectin (7,8). Recent studies have implicated several members of matricellular proteins, such as osteopontin, secreted protein acidic and rich in cysteine, and angiopoietin-like 4 (ANGPTL4) as important factors in tumor progression (4,(9)(10)(11).…”