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  • Secreted phosphoprotein 1 (SPP1, osteopontin) binds to integrin alpha v beta 6 on porcine trophectoderm cells and integrin alpha v beta 3 on uterine luminal epithelial cells, and promotes trophectoderm cell adhesion and migration.

Secreted phosphoprotein 1 (SPP1, osteopontin) binds to integrin alpha v beta 6 on porcine trophectoderm cells and integrin alpha v beta 3 on uterine luminal epithelial cells, and promotes trophectoderm cell adhesion and migration.

Biology of reproduction (2009-07-03)
David W Erikson, Robert C Burghardt, Kayla J Bayless, Greg A Johnson
ABSTRACT

Conceptus implantation involves pregnancy-specific alterations in extracellular matrix at the conceptus-maternal interface. Secreted phosphoprotein 1 (SPP1, osteopontin) is induced just before implantation and is present at the conceptus-maternal interface in mammals. In the present study, we investigated mechanisms by which SPP1 facilitates porcine conceptus and uterine luminal epithelial cell attachment. Native bovine milk and wild-type rat recombinant SPP1 stimulated trophectoderm cell migration. Bovine milk SPP1, ovine uterine SPP1, and recombinant wild-type, but not mutated, rat SPP1 promoted dose- and cation-dependent attachment of porcine trophectoderm and uterine luminal epithelial cells, which was markedly reduced in the presence of a linear Arg-Gly-Asp integrin-blocking peptide. Affinity chromatography and immunoprecipitation experiments revealed direct binding of alpha v beta 6 trophectoderm and alpha v beta 3 uterine epithelial cell integrins to SPP1. Immunofluorescence microscopy using SPP1-coated microspheres revealed colocalization of the alpha v integrin subunit and talin at focal adhesions as well as at the apical domain of trophectoderm cells. Similarly, immunofluorescence staining of implantation sites in frozen gravid uterine cross sections localized SPP1 and alpha v integrin to the apical surfaces of trophectoderm and luminal epithelium and beta 3 integrin to the apical surface of luminal epithelium. To our knowledge, the present study is the first to demonstrate functionally that SPP1 directly binds specific integrins to promote trophectoderm cell migration and attachment to luminal epithelium that may be critical to conceptus elongation and implantation.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Monoclonal Anti-Talin antibody produced in mouse, clone 8d4, ascites fluid
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Anti-Integrin αVβ3 Antibody, clone LM609, Azide Free, clone LM609, Chemicon®, from mouse
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Anti-Integrin αVβ5 Antibody, clone P1F6, clone P1F6, Chemicon®, from mouse
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Anti-Integrin α5 Antibody, CT, Intracellular, serum, Chemicon®
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Anti-Integrin β6 Antibody, clone CSβ6, azide free, clone CSbeta6, Chemicon®, from mouse
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Anti-Integrin alphaV Antibody, CT, Intracellular, serum, Chemicon®
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Anti-Integrin α4 Antibody, cytoplasmic on CT, serum, Chemicon®
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Anti-Integrin β3 Antibody, cytoplasmic domain, serum, Chemicon®
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Anti-α-Actinin antibody produced in rabbit, whole antiserum