Biomedical subjects

Mary M Zutter

Publications and source records attributed to Mary M Zutter.

10 recordsLinked to original sources

PubMed2006

Wound healing in the alpha2beta1 integrin-deficient mouse: altered keratinocyte biology and dysregulated matrix metalloproteinase expression.

The alpha2beta1 integrin, a collagen/laminin receptor, is expressed at high level in the basal cell layer of the epidermis. To define the role of the alpha2beta1 integrin in wound healing, wound repair was extensively evaluated in wild-type and alpha2-null mice in vivo. In addition, the impact of alpha2beta1 integrin-deficiency on the function of primary murine keratinocytes in vitro was analyzed. Our in vivo findings demonstrate that genetic deletion of the alpha2beta1 integrin does not significantly alter the rate of re-epithelialization, collagen deposition, or tensile strength during wound closure in mice. In marked contrast to the observed similarities in wound healing, deletion of the alpha2beta1 integrin resulted in a dramatic increase in neoangiogenesis in the wound microenvironment. In contrast to in vivo studies, primary keratinocytes from alpha2-null mice adhered poorly and displayed impaired migration on type I collagen in vitro. We demonstrate that alpha2beta1 integrin-ligation negatively regulates expression of genes including matrix metalloproteinases both in vivo and in vitro. Furthermore, the changes in gene expression could potentially account for relatively normal wound healing in the alpha2-deficient mouse and our recent observation that suggests an antiangiogenic role for the alpha2beta1 integrin in vivo.

Animals↗

PubMed2006

Beta1 integrin mediates internalization of mammalian reovirus.

Reovirus infection is initiated by interactions between the attachment protein sigma1 and cell surface carbohydrate and junctional adhesion molecule A (JAM-A). Expression of a JAM-A mutant lacking a cytoplasmic tail in nonpermissive cells conferred full susceptibility to reovirus infection, suggesting that cell surface molecules other than JAM-A mediate viral internalization following attachment. The presence of integrin-binding sequences in reovirus outer capsid protein lambda2, which serves as the structural base for sigma1, suggests that integrins mediate reovirus endocytosis. A beta1 integrin-specific antibody, but not antibodies specific for other integrin subunits, inhibited reovirus infection of HeLa cells. Expression of a beta1 integrin cDNA, along with a cDNA encoding JAM-A, in nonpermissive chicken embryo fibroblasts conferred susceptibility to reovirus infection. Infectivity of reovirus was significantly reduced in beta1-deficient mouse embryonic stem cells in comparison to isogenic cells expressing beta1. However, reovirus bound equivalently to cells that differed in levels of beta1 expression, suggesting that beta1 integrins are involved in a postattachment entry step. Concordantly, uptake of reovirus virions into beta1-deficient cells was substantially diminished in comparison to viral uptake into beta1-expressing cells. These data provide evidence that beta1 integrin facilitates reovirus internalization and suggest that viral entry occurs by interactions of reovirus virions with independent attachment and entry receptors on the cell surface.

Amino Acid Sequence↗

PubMed2005

Novel collectin/C1q receptor mediates mast cell activation and innate immunity.

Mast cells play a critical role in innate immunity, allergy, and autoimmune diseases. The receptor/ligand interactions that mediate mast cell activation are poorly defined. The alpha2beta1 integrin, a receptor for collagens, laminins, decorin, E-cadherin, matrix metalloproteinase-1 (MMP-1), endorepellin, and several viruses, has been implicated in normal developmental, inflammatory, and oncogenic processes. We recently reported that alpha2 integrin subunit-deficient mice exhibited markedly diminished neutrophil and IL-6 responses during Listeria monocytogenes- and zymosan-induced peritonitis. Peritoneal mast cells require alpha2beta1 integrin expression for activation in response to pathogens, yet the ligand and molecular mechanisms by which the alpha2beta1 integrin induces activation and cytokine secretion remain unknown. We now report that the alpha2beta1 integrin is a novel receptor for multiple collectins and the C1q complement protein. We demonstrate that the alpha2beta1 integrin provides a costimulatory function required for mast cell activation and cytokine secretion. This finding suggests that the alpha2beta1 integrin is not only important for innate immunity but may serve as a critical target for the regulation of autoimmune/allergic disorders.

Animals↗

PubMed2005

GPVI and alpha2beta1 play independent critical roles during platelet adhesion and aggregate formation to collagen under flow.

The roles of the 2 major platelet-collagen receptors, glycoprotein VI (GPVI) and integrin alpha2beta1, have been intensely investigated using a variety of methods over the past decade. In the present study, we have used pharmacologic and genetic approaches to study human and mouse platelet adhesion to collagen under flow conditions. Our studies demonstrate that both GPVI and integrin alpha2beta1 play significant roles for platelet adhesion to collagen under flow and that the loss of both receptors completely ablates this response. Intracellular signaling mediated by the cytoplasmic adaptor Src homology 2 domain-containing leukocyte protein of 76 kDa (SLP-76) but not by the transmembrane adaptor linker for activation of T cells (LAT) is critical for platelet adhesion to collagen under flow. In addition, reduced GPVI receptor density results in severe defects in platelet adhesion to collagen under flow. Defective adhesion to collagen under flow is associated with prolonged tail-bleeding times in mice lacking one or both collagen receptors. These studies establish platelet-collagen responses under physiologic flow as the consequence of a close partnership between 2 structurally distinct receptors and suggest that both receptors play significant hemostatic roles in vivo.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Endorepellin causes endothelial cell disassembly of actin cytoskeleton and focal adhesions through alpha2beta1 integrin.

Endorepellin, the COOH-terminal domain of the heparan sulfate proteoglycan perlecan, inhibits several aspects of angiogenesis. We provide evidence for a novel biological axis that links a soluble fragment of perlecan protein core to the major cell surface receptor for collagen I, alpha2beta1 integrin, and provide an initial investigation of the intracellular signaling events that lead to endorepellin antiangiogenic activity. The interaction between endorepellin and alpha2beta1 integrin triggers a unique signaling pathway that causes an increase in the second messenger cAMP; activation of two proximal kinases, protein kinase A and focal adhesion kinase; transient activation of p38 mitogen-activated protein kinase and heat shock protein 27, followed by a rapid down-regulation of the latter two proteins; and ultimately disassembly of actin stress fibers and focal adhesions. The end result is a profound block of endothelial cell migration and angiogenesis. Because perlecan is present in both endothelial and smooth muscle cell basement membranes, proteolytic activity during the initial stages of angiogenesis could liberate antiangiogenic fragments from blood vessels' walls, including endorepellin.

Actins↗

PubMed2004

Proteases, extracellular matrix, and cancer: a workshop of the path B study section.

The role of the extracellular matrix (ECM) in the tumor microenvironment is not limited to being a barrier against tumor invasion. The ECM is a reservoir of cell binding proteins and growth factors that affect tumor cell behavior. It is also substantially modified by proteases produced by tumor cells or stroma cells. As a result of the activity of these proteases, cell-cell and cell-ECM interactions are altered, new biologically active ECM molecules are generated, and the bioavailability and activity of many growth factors, growth factor receptors, and cytokines are modified. ECM-degrading proteases also play a critical role in angiogenesis, where they can act as positive as well as negative regulators of endothelial cell proliferation and vascular morphogenesis. This review article summarizes some of the most relevant findings made over the recent years that were discussed at a workshop organized by the Path B Study Section of the National Institutes of Health in October 2002.

Animals↗

PubMed2003

Mast cell-mediated inflammatory responses require the alpha 2 beta 1 integrin.

Although the alpha 2 beta 1 integrin is widely expressed and has been extensively studied, it has not been previously implicated in mast cell biology. We observed that alpha 2 integrin subunit-deficient mice exhibited markedly diminished neutrophil and interleukin-6 responses during Listeria monocytogenes- and zymosan-induced peritonitis. Since exudative neutrophils of wild-type mice expressed little alpha 2 beta 1 integrin, it seemed unlikely that this integrin mediated neutrophil migration directly. Here, we demonstrate constitutive alpha 2 beta 1 integrin expression on peritoneal mast cells. Although alpha 2-null mice contain normal numbers of peritoneal mast cells, these alpha 2-null cells do not support in vivo mast cell-dependent inflammatory responses. We conclude that alpha 2 beta 1 integrin provides a costimulatory function required for mast cell activation and cytokine production in response to infection.

Animals↗

PubMed2003

Alpha2beta1 integrin and development of atherosclerosis in a mouse model: assessment of risk.

OBJECTIVE: The alpha2beta1 integrin serves as a collagen or collagen/laminin receptor on many cell types, including endothelial cells and platelets. Many studies indicate that the alpha2beta1 integrin is a critical mediator of platelet adhesion to collagen. Epidemiologic studies suggest a direct correlation between the genetically determined platelet surface density of the alpha2beta1 integrin and the risk of thrombotic diseases, such as myocardial infarction and stroke, in the young, which are well-established complications of atherosclerosis. We have now used the alpha2beta1 integrin-deficient mouse to evaluate the contributions of the alpha2beta1 integrin to the development of atherosclerosis. METHODS AND RESULTS: We generated wild-type (alpha2+/+) or alpha2beta1 integrin-deficient (alpha2-/-) mice that were also deficient in the apolipoprotein E (ApoE) gene (ApoE-/-) and compared atherosclerotic lesion development in alpha2+/+ ApoE-/- and alpha2-/- ApoE-/- mice that were fed a high-fat, cholesterol-containing diet for 6 or 15 weeks. Total lesional area did not differ significantly between the alpha2-null animals and the wild-type animals at either 6 or 15 weeks. CONCLUSIONS: Our results suggest that risk for arterial thrombotic disease associated with high-level alpha2beta1 integrin expression is not attributable to enhanced development of atherosclerosis per se but may rather be a consequence of thrombotic complications at the plaques.

Animals↗

PubMed2003

The contributions of the alpha 2 beta 1 integrin to vascular thrombosis in vivo.

The alpha 2 beta 1 integrin serves as a receptor for collagens, laminin, and several other nonmatrix ligands. Many studies have suggested that the alpha 2 beta 1 integrin is a critical mediator of platelet adhesion to collagen within the vessel wall after vascular injury and that the interactions of the platelet alpha 2 beta 1 integrin with subendothelial collagen after vascular injury are required for proper hemostasis. We have used the alpha 2 beta 1 integrin-deficient mouse to evaluate the contributions of the alpha 2 beta 1 integrin in 2 in vivo models of thrombosis. Studies using a model of endothelial injury to the carotid artery reveal that the alpha 2 beta 1 integrin plays a critical role in vascular thrombosis at the blood-vessel wall interface under flow conditions. In contrast, the alpha 2 beta 1 integrin is not required for the formation of thrombi and pulmonary emboli following intravascular injection of collagen. Our results are the first to document a critical in vivo role for the alpha 2 beta 1 integrin in thrombus formation at the vessel wall under conditions of shear following vascular injury.

Animals↗

PubMed2002

The alpha(2) integrin subunit-deficient mouse: a multifaceted phenotype including defects of branching morphogenesis and hemostasis.

The alpha(2)beta(1) integrin is a collagen/laminin receptor expressed on platelets, endothelial cells, fibroblasts, and epithelial cells. To define the role of the alpha(2)beta(1) integrin in vivo, we created a genetically engineered mouse in which expression of the alpha(2)beta(1) integrin was completely eliminated. Mice deficient in the alpha(2)beta(1) integrin are viable, fertile, and develop normally with no excess lethality of homozygotes. Both alpha(2)beta(1)-integrin protein and alpha(2) mRNA were undetectable in the alpha(2)-null mice. Gross and histological evaluation of the heart, lungs, kidneys, gastrointestinal tract, pancreas, skin, and reproductive tracts revealed no abnormalities. However, quantitative analysis of mammary gland branching morphogenesis demonstrated that branching complexity is markedly diminished in the alpha(2)-deficient animals. Studies in the alpha(2)-deficient animals do not support the proposed roles for the alpha(2)beta(1) integrin on fibroblasts and keratinocytes in wound healing. When compared to platelets from wild-type littermates, platelets from alpha(2)-null mice failed to adhere to type I collagen under either static or shear-stress conditions. Although platelets from alpha(2)-deficient animals aggregated in response to collagen, they did so with prolonged lag time and lessened intensity. The alpha(2)beta(1) integrin-null mouse thus exhibits diverse, sometimes subtle, phenotypes consistent with the widespread pattern of alpha(2)beta(1) integrin expression.

Animals↗