Integrin αvβ5 in endothelial cells of rat splenic sinus: an immunohistochemical and ultrastructural study

Abstract

Localization of integrins β1-8, α1, α2, α3, α5, α6 and αv in sinus endothelial cells of the rat spleen was examined by immunofluorescence microscopy. Labeling for anti-integrin β5 and integrin αv was detected and colocalized in the entire circumference of endothelial cells. Labeling for integrin β5, vinculin and actin filaments demonstrated that they lay close to each other in the basal part of the endothelial cells. Although the other integrin βs, including integrin β1 and integrins α1, α2, α3, α5 and α6 in combination with integrin β1, were localized in leukocytes, slightly large cells, megakaryocytes and/or platelets in the sinus lumen and splenic cords, they were not detected in endothelial cells. Labeling for vitronectin, a component of the extracellular-matrix-binding integrin αvβ5, was strongly stained in the periphery of the wall of sinuses, as was collagen IV and, in addition, was localized in the cytoplasm of endothelial cells. Ultrastructural localization of integrin β5, vitronectin and clathrin was examined by immunogold electron microscopy to elucidate the involvement of integrin αvβ5 in the endocytosis of vitronectin in sinus endothelial cells. Electron microscopy with detergent extraction revealed abundant coated pits and coated vesicles in endothelial cells. Immunogold labeling for vitronectin was present in pits, vesicles and the stacked endoplasmic reticulum. Double-labeling for integrin β5 or integrin αv and clathrin revealed that they were colocalized in some vesicles in close proximity to the apical and lateral plasma membrane of the endothelial cells. The possible functional roles of integrin αvβ5 in endothelial cells of the splenic sinus are discussed.

NPNT is Expressed by Osteoblasts and Mediates Angiogenesis via the Activation of Extracellular Signal-regulated Kinase

“…Indeed, NPNT has been reported to be a major ligand for α 8 β 1 integrin, and has lower binding affinities to other integrins such as α v β 3 , α v β 5 , α v β 6 and α 4 β 7 13. Although the data regarding the presence of α 8 β 1 integrin on endothelial cells is currently lacking, many vascular-related integrin receptors have been reported on endothelial cells, including α 1 β 1 , α 2 β 1 36, α v β 5 37, α 5 β 1 38 and α v β 3 39. In addition, previous studies have demonstrated that EGFL7, a potent EGF-like angiogenic factor, mediates angiogenesis through the binding of α v β 3 integrin and the activation of integrin-associated signalling cascades2140.…”

Phosphatidylserine receptors: Enhancers of enveloped virus entry and infection

“…Baculovirus: Mouse: Mammary glands (Oshima et al, 1999;Stubbs et al, 1990), spleen, lymph node, brain Garmy-Susini et al, 2007;Uehara and Uehara, 2014), and vascular system (Silvestre et al, 2005;Brooks et al, 1994) Autographa californica multicapsid nucleopolyhedrovirus (Morizono and Chen, 2014) COMMA-1D, D1, P388D1 Thery et al, 1999;Oshima et al, 2002)…”

“…Expression of MFG-E8/integrin αvβ5 and TIM-4 has been detected in spleen (Meyers et al, 2005;Uehara and Uehara, 2014). In particular, TIM-4 is expressed on splenic macrophages (Kobayashi et al, 2007;Wong et al, 2010), a target of flaviviruses (Balsitis et al, 2009).…”

Inhibition of αvβ5 Integrin Attenuates Vascular Permeability and Protects against Renal Ischemia-Reperfusion Injury

“…10 avb5 has been reported to be expressed in multiple cell types in vitro, including endothelial cells, epithelial cells, fibroblasts, and various leukocyte lineages. [11][12][13][14][15] A number of biologic functions have been attributed to avb5, ranging from tumor angiogenesis 16 and phagocytosis 17 to adenoviral uptake, 18 fatty acid uptake, 19 and retinal pigment epithelium homeostasis. 20 Several studies have also demonstrated a role of avb5 in regulating vascular barrier integrity.…”