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Laminin polymerization induces a receptor-cytoskeleton network.

Colognato H, Winkelmann DA, Yurchenco PD - J. Cell Biol. (1999)

Bottom Line: We found that on muscle cell surfaces, laminins preferentially polymerize while bound to receptors that included dystroglycan and alpha7beta1 integrin.As a result, dystroglycan and integrin redistribute into a reciprocal network as do cortical cytoskeleton components vinculin and dystrophin.Preferential polymerization of laminin on cell surfaces, and the resulting induction of cortical architecture, is a cooperative process requiring laminin- receptor ligation, receptor-facilitated self-assembly, actin reorganization, and signaling events.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.

ABSTRACT
The transition of laminin from a monomeric to a polymerized state is thought to be a crucial step in the development of basement membranes and in the case of skeletal muscle, mutations in laminin can result in severe muscular dystrophies with basement membrane defects. We have evaluated laminin polymer and receptor interactions to determine the requirements for laminin assembly on a cell surface and investigated what cellular responses might be mediated by this transition. We found that on muscle cell surfaces, laminins preferentially polymerize while bound to receptors that included dystroglycan and alpha7beta1 integrin. These receptor interactions are mediated through laminin COOH-terminal domains that are spatially and functionally distinct from NH2-terminal polymer binding sites. This receptor-facilitated self-assembly drives rearrangement of laminin into a cell-associated polygonal network, a process that also requires actin reorganization and tyrosine phosphorylation. As a result, dystroglycan and integrin redistribute into a reciprocal network as do cortical cytoskeleton components vinculin and dystrophin. Cytoskeletal and receptor reorganization is dependent on laminin polymerization and fails in response to receptor occupancy alone (nonpolymerizing laminin). Preferential polymerization of laminin on cell surfaces, and the resulting induction of cortical architecture, is a cooperative process requiring laminin- receptor ligation, receptor-facilitated self-assembly, actin reorganization, and signaling events.

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Laminin uses its COOH-terminal long arm to bind to the myotube surface. (A) Structure/function map of laminin proteolytic  fragments and recombinant proteins, shown as a composite of features common to laminin-1 (α1β1γ1) and laminin-2 (α2β1γ1). Proteolytic fragments include: E1′, E4, E8, and E3. Recombinant proteins include: α1(VI-IVb), α2(VI-IVb), and α2(G). Receptor binding  sites are: α1β1, α2β1, α7β1 integrin, and α-dystroglycan (αDG). Binding sites for extracellular matrix molecules: laminin polymer– forming regions (domains V and VI of α-, β-, and γ-short arms), entactin/nidogen (En/Nd), and agrin. Mutations used include the following: 57–amino acid region deleted in α2 chain of dystrophic dy2J mouse (Δdy2J). (B) Direct binding of laminin COOH-terminal long  arm proteins to the myotube surface. Laminin-1 and laminin-2 bound myotubes and formed a reticular pattern after 1 h (insets). Recombinant laminin α-subunit proteins from the NH2-terminal short arm region (α1- and α2[VI-IVb]′) showed no detectable binding.  COOH-terminal proteins, including proteolytic fragments E8 and E3, and recombinant α2-G domain protein showed widespread attachment to the myotube surface, but remained in a diffuse, punctate distribution. Insets show regions at two times the magnification.
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Figure 2: Laminin uses its COOH-terminal long arm to bind to the myotube surface. (A) Structure/function map of laminin proteolytic fragments and recombinant proteins, shown as a composite of features common to laminin-1 (α1β1γ1) and laminin-2 (α2β1γ1). Proteolytic fragments include: E1′, E4, E8, and E3. Recombinant proteins include: α1(VI-IVb), α2(VI-IVb), and α2(G). Receptor binding sites are: α1β1, α2β1, α7β1 integrin, and α-dystroglycan (αDG). Binding sites for extracellular matrix molecules: laminin polymer– forming regions (domains V and VI of α-, β-, and γ-short arms), entactin/nidogen (En/Nd), and agrin. Mutations used include the following: 57–amino acid region deleted in α2 chain of dystrophic dy2J mouse (Δdy2J). (B) Direct binding of laminin COOH-terminal long arm proteins to the myotube surface. Laminin-1 and laminin-2 bound myotubes and formed a reticular pattern after 1 h (insets). Recombinant laminin α-subunit proteins from the NH2-terminal short arm region (α1- and α2[VI-IVb]′) showed no detectable binding. COOH-terminal proteins, including proteolytic fragments E8 and E3, and recombinant α2-G domain protein showed widespread attachment to the myotube surface, but remained in a diffuse, punctate distribution. Insets show regions at two times the magnification.

Mentions: First, we sought to determine which regions of the large multisubunit laminin molecule interacted directly with the myotube cell surface (Fig. 2). A battery of laminin proteolytic fragments and recombinant laminin domains was evaluated to determine which domains bound directly to myotube cell surface receptors. Here we considered the binding properties of both α1- and α2-chain–containing laminins, shown together in a composite model (Fig. 2 A). This model depicts the boundaries of laminin fragments and some of the sites known to interact with receptors and extracellular matrix molecules.


Laminin polymerization induces a receptor-cytoskeleton network.

Colognato H, Winkelmann DA, Yurchenco PD - J. Cell Biol. (1999)

Laminin uses its COOH-terminal long arm to bind to the myotube surface. (A) Structure/function map of laminin proteolytic  fragments and recombinant proteins, shown as a composite of features common to laminin-1 (α1β1γ1) and laminin-2 (α2β1γ1). Proteolytic fragments include: E1′, E4, E8, and E3. Recombinant proteins include: α1(VI-IVb), α2(VI-IVb), and α2(G). Receptor binding  sites are: α1β1, α2β1, α7β1 integrin, and α-dystroglycan (αDG). Binding sites for extracellular matrix molecules: laminin polymer– forming regions (domains V and VI of α-, β-, and γ-short arms), entactin/nidogen (En/Nd), and agrin. Mutations used include the following: 57–amino acid region deleted in α2 chain of dystrophic dy2J mouse (Δdy2J). (B) Direct binding of laminin COOH-terminal long  arm proteins to the myotube surface. Laminin-1 and laminin-2 bound myotubes and formed a reticular pattern after 1 h (insets). Recombinant laminin α-subunit proteins from the NH2-terminal short arm region (α1- and α2[VI-IVb]′) showed no detectable binding.  COOH-terminal proteins, including proteolytic fragments E8 and E3, and recombinant α2-G domain protein showed widespread attachment to the myotube surface, but remained in a diffuse, punctate distribution. Insets show regions at two times the magnification.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2185083&req=5

Figure 2: Laminin uses its COOH-terminal long arm to bind to the myotube surface. (A) Structure/function map of laminin proteolytic fragments and recombinant proteins, shown as a composite of features common to laminin-1 (α1β1γ1) and laminin-2 (α2β1γ1). Proteolytic fragments include: E1′, E4, E8, and E3. Recombinant proteins include: α1(VI-IVb), α2(VI-IVb), and α2(G). Receptor binding sites are: α1β1, α2β1, α7β1 integrin, and α-dystroglycan (αDG). Binding sites for extracellular matrix molecules: laminin polymer– forming regions (domains V and VI of α-, β-, and γ-short arms), entactin/nidogen (En/Nd), and agrin. Mutations used include the following: 57–amino acid region deleted in α2 chain of dystrophic dy2J mouse (Δdy2J). (B) Direct binding of laminin COOH-terminal long arm proteins to the myotube surface. Laminin-1 and laminin-2 bound myotubes and formed a reticular pattern after 1 h (insets). Recombinant laminin α-subunit proteins from the NH2-terminal short arm region (α1- and α2[VI-IVb]′) showed no detectable binding. COOH-terminal proteins, including proteolytic fragments E8 and E3, and recombinant α2-G domain protein showed widespread attachment to the myotube surface, but remained in a diffuse, punctate distribution. Insets show regions at two times the magnification.
Mentions: First, we sought to determine which regions of the large multisubunit laminin molecule interacted directly with the myotube cell surface (Fig. 2). A battery of laminin proteolytic fragments and recombinant laminin domains was evaluated to determine which domains bound directly to myotube cell surface receptors. Here we considered the binding properties of both α1- and α2-chain–containing laminins, shown together in a composite model (Fig. 2 A). This model depicts the boundaries of laminin fragments and some of the sites known to interact with receptors and extracellular matrix molecules.

Bottom Line: We found that on muscle cell surfaces, laminins preferentially polymerize while bound to receptors that included dystroglycan and alpha7beta1 integrin.As a result, dystroglycan and integrin redistribute into a reciprocal network as do cortical cytoskeleton components vinculin and dystrophin.Preferential polymerization of laminin on cell surfaces, and the resulting induction of cortical architecture, is a cooperative process requiring laminin- receptor ligation, receptor-facilitated self-assembly, actin reorganization, and signaling events.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.

ABSTRACT
The transition of laminin from a monomeric to a polymerized state is thought to be a crucial step in the development of basement membranes and in the case of skeletal muscle, mutations in laminin can result in severe muscular dystrophies with basement membrane defects. We have evaluated laminin polymer and receptor interactions to determine the requirements for laminin assembly on a cell surface and investigated what cellular responses might be mediated by this transition. We found that on muscle cell surfaces, laminins preferentially polymerize while bound to receptors that included dystroglycan and alpha7beta1 integrin. These receptor interactions are mediated through laminin COOH-terminal domains that are spatially and functionally distinct from NH2-terminal polymer binding sites. This receptor-facilitated self-assembly drives rearrangement of laminin into a cell-associated polygonal network, a process that also requires actin reorganization and tyrosine phosphorylation. As a result, dystroglycan and integrin redistribute into a reciprocal network as do cortical cytoskeleton components vinculin and dystrophin. Cytoskeletal and receptor reorganization is dependent on laminin polymerization and fails in response to receptor occupancy alone (nonpolymerizing laminin). Preferential polymerization of laminin on cell surfaces, and the resulting induction of cortical architecture, is a cooperative process requiring laminin- receptor ligation, receptor-facilitated self-assembly, actin reorganization, and signaling events.

Show MeSH
Related in: MedlinePlus