Protein Kinase B/Akt Acts via Glycogen Synthase Kinase 3 To Regulate Recycling of αvβ3 and α5β1 Integrins

129

153

A dynamic cell-matrix interaction is crucial for a rapid cellular response to changes in the environment. Appropriate cell behavior in response to the changing wound environment is required for efficient wound closure. However, the way in which wound keratinocytes modify the wound environment to coordinate with such cellular responses remains less studied. We demonstrated that angiopoietin-like 4 (ANGPTL4) produced by wound keratinocytes coordinates cell-matrix communication. ANGPTL4 interacts with vitronectin and fibronectin in the wound bed, delaying their proteolytic degradation by metalloproteinases. This interaction does not interfere with integrinmatrix protein recognition and directly affects cell-matrix communication by altering the availability of intact matrix proteins. These interactions stimulate integrin-focal adhesion kinase, 14-3-3, and PKC-mediated signaling pathways essential for effective wound healing. The deficiency of ANGPTL4 in mice delays wound re-epithelialization. Further analysis revealed that cell migration was impaired in the ANGPTL4-deficient keratinocytes. Altogether, the findings provide molecular insight into a novel control of wound healing via ANGPTL4-dependent regulation of cell-matrix communication. Given the known role of ANGPTL4 in glucose and lipid homeostasis, it is a prime therapeutic candidate for the treatment of diabetic wounds. It also underscores the importance of cell-matrix communication during angiogenesis and cancer metastasis.Skin repair after an injury proceeds via a finely tuned pattern of integrated biological events aimed at restoration of the epithelial barrier. The inflammatory stage of repair is followed by the proliferation and migration of keratinocytes, a process called re-epithelialization (1). These events are regulated spatiotemporally by several classical growth factors and cytokines, the effects of which have been well documented (2). Less studied are extracellular factors such as matricellular proteins and adipocytokines, both shown to have a profound local impact during wound repair (3, 4). Effective directed cell migration requires constant cellular interaction with the extracellular matrix (ECM) 3 in response to the changing wound environment. Although the importance of such cell-matrix communication in wound healing is well recognized, the mechanism that modifies the external wound microenvironment for coordinated keratinocyte behavior remains unclear.Integrins on the cell surface often function as biosensors to constantly interrogate the wound environment and modulate cell responses accordingly. Binding of integrins to their cognate matrix proteins activates intracellular signaling pathways that modulate a broad range of cellular processes, including cell migration (5). Integrin-mediated signaling requires that integrins bind substrate-anchored matrix proteins. This interaction provides mechanical resistance that permits tensional forces to be generated via the actomyosin system (6). In contrast, small soluble matrix protein fragments gene...

Section: Angptl4 Interacts With Matrix Proteins and Delaysmentioning

confidence: 64%

Angiopoietin-like 4 Interacts with Matrix Proteins to Modulate Wound Healing*

Goh

Pal

Chong

et al. 2010

129

153

“…Dominant negative construct of IB␣ (pCMV-IB␣M) was purchased from Clontech (Mountain View, CA). Human MMP-13 promoter construct and plasmid expression vector containing siRNA targeting Akt (Mu6pro-Akt1/2) and control siRNA plasmid construct (Mu6pro) were previously described (27,29,30). The p3xNFBLuc plasmid construct, containing three copies of tandemly repeated NFB response element sequences (5Ј-TTG-GGCACTCCCTG-3Ј) of MMP-13 promoter region was achieved by placing the NFB response elements of MMP-13 promoter region upstream of an SV40 promoter at the SacI site of the pGL3-promoter vector, which contains a luciferase reporter gene system (Promega) as described previously (31).…”

Section: Methodsmentioning

confidence: 99%

Basic Fibroblast Growth Factor Activates the MAPK and NFκB Pathways That Converge on Elk-1 to Control Production of Matrix Metalloproteinase-13 by Human Adult Articular Chondrocytes

Muddasani¹,

Norman

Ellman

et al. 2007

Self Cite

122

The pathology of joint destruction is associated with elevated production of basic fibroblast growth factor (bFGF) and matrix metalloproteinase-13 (MMP-13). In osteoarthritic joint disease, expression of bFGF and MMP-13 in chondrocytes and their release into the synovial fluid are significantly increased. We have previously found that the capacity for cartilage repair in human adult articular chondrocytes is severely compromised by minimal exposure to bFGF because bFGF reduces responsiveness to bone morphogenetic protein-7 and insulin-like growth factor-1 and induces MMP-13 through protein kinase C␦-dependent activation of multiple mitogen-activated protein kinase (MAPK) signaling pathways. Here we show using biochemical and molecular approaches that transcription factor Elk-1, a direct downstream target of MAPK, is a critical transcriptional activator of of MMP-13 by bFGF in human articular chondrocytes. We also provide evidence that Elk-1 is a direct target of NFB and induces MMP-13 expression upon activation of the NFB signaling pathway. Taken together, our results suggest that elevated expression of MMP-13 occurs through Elk-1 activation of both MAPK and NFB signaling pathways, thus revealing a two-pronged biological mechanism by which bFGF controls the production of catabolic enzymes that are associated with excessive degradation of the cartilage matrix in degenerative joint diseases such as osteoarthritis.

“…Similarly, our recent study showed that kallikrein gene delivery protects against cerebral ischemia injury and apoptosis along with activation of Akt signaling (6). Activation of Akt triggers downstream signaling pathways such as GSK-3 phosphorylation in a variety of cell lines (7). GSK activity is inactivated by Akt-induced phosphorylation at serine 21 (␣ isoform) and serine 9 (␤ isoform), leading to inhibition of apoptosis in insulin-mediated signal transduction (8,9).…”

mentioning

confidence: 99%

Kallikrein/Kinin Protects against Myocardial Apoptosis after Ischemia/Reperfusion via Akt-Glycogen Synthase Kinase-3 and Akt-Bad·14-3-3 Signaling Pathways

Yin

Chao

2005

109

Our previous study has shown that human tissue kallikrein protected against ischemia/reperfusion-induced myocardial injury. In the present study, we investigated the protective role of local kallikrein gene delivery in ischemia/reperfusion-induced cardiomyocyte apoptosis and its signaling mechanisms in promoting cardiomyocyte survival. Adenovirus carrying the human tissue kallikrein gene was delivered locally into the heart using a catheter-based technique. Expression and localization of recombinant human kallikrein in rat myocardium after gene transfer were determined immunohistochemically. Kallikrein gene delivery markedly reduced reperfusion-induced cardiomyocyte apoptosis identified by both in situ nick end-labeling and DNA fragmentation. Delivery of the kallikrein gene increased phosphorylation of Src, Akt, glycogen synthase kinase (GSK)-3␤, and Bad(Ser-136) but reduced caspase-3 activation in rat myocardium after reperfusion. The protective effect of kallikrein on apoptosis and its signaling mediators was blocked by icatibant and dominant-negative Akt, indicating a kinin B2 receptor-Akt-mediated event. Similarly, kinin or transduction of kallikrein in cultured cardiomyocytes promoted cell viability and attenuated apoptosis induced by hypoxia/reoxygenation. The effect of kallikrein on cardiomyocyte survival was blocked by dominant-negative Akt and a constitutively active mutant of GSK-3␤, but it was facilitated by constitutively active Akt, catalytically inactive GSK-3␤, lithium, and caspase-3 inhibitor. Moreover, kallikrein promoted Bad⅐14-3-3 complex formation and inhibited Akt-GSK-3␤-dependent activation of caspase-3, whereas caspase-3 administration caused reduction of the Bad⅐14-3-3 complex, indicating an interaction between Akt-GSK-caspase-3 and Akt-Bad⅐14-3-3 signaling pathways. In conclusion, kallikrein/kinin protects against cardiomyocyte apoptosis in vivo and in vitro via Akt-Bad⅐14-3-3 and Akt-GSK-3␤-caspase-3 signaling pathways.