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J. Cell Biol.,
Volume 144, Number 3, February 8, 1999 549-561
6
1 Interact with
Laminin and an ADAM


* Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908; and Integrins can exist in different functional
states with low or high binding capacity for particular
ligands. We previously provided evidence that the integrin
Beth Israel Deaconess Medical
Center, Harvard Medical School, Boston, Massachusetts 02115
6
1, on mouse eggs and on
6-transfected cells,
interacted with the disintegrin domain of the sperm surface protein ADAM 2 (fertilin
). In the present study
we tested the hypothesis that different states of
6
1
interact with fertilin and laminin, an extracellular matrix ligand for
6
1. Using
6-transfected cells we
found that treatments (e.g., with phorbol myristate acetate or MnCl2) that increased adhesion to laminin inhibited sperm binding. Conversely, treatments that inhibited laminin adhesion increased sperm binding.
Next, we compared the ability of fluorescent beads
coated with either fertilin
or with the laminin E8 fragment to bind to eggs. In Ca2+-containing media, fertilin
beads bound to eggs via an interaction mediated by
the disintegrin loop of fertilin
and by the
6 integrin subunit. In Ca2+-containing media, laminin E8 beads
did not bind to eggs. Treatment of eggs with phorbol
myristate acetate or with the actin disrupting agent, latrunculin A, inhibited fertilin bead binding, but did not
induce laminin E8 bead binding. Treatment of eggs
with Mn2+ dramatically increased laminin E8 bead
binding, and inhibited fertilin bead binding. Our results
provide the first evidence that different states of an integrin (
6
1) can interact with an extracellular matrix
ligand (laminin) or a membrane-anchored cell surface
ligand (ADAM 2).
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