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Laminin-sulfatide binding initiates basement membrane assembly and enables receptor signaling in Schwann cells and fibroblasts.

Li S, Liquari P, McKee KK, Harrison D, Patel R, Lee S, Yurchenco PD - J. Cell Biol. (2005)

Bottom Line: This glycolipid anchors Lm-1 and -2 to SC surfaces by binding to their LG domains and enables basement membrane (BM) assembly.Revealingly, non-BM-forming fibroblasts become competent for BM assembly when sulfatides are intercalated into their cell surfaces.Collectively, our findings suggest that sulfated glycolipids are key Lm anchors that determine which cell surfaces can assemble Lms to initiate BM assembly and DG- and integrin-mediated signaling.

View Article: PubMed Central - PubMed

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

ABSTRACT
Endoneurial laminins (Lms), beta1-integrins, and dystroglycan (DG) are important for Schwann cell (SC) ensheathment and myelination of axons. We now show that SC expression of galactosyl-sulfatide, a Lm-binding glycolipid, precedes that of Lms in developing nerves. This glycolipid anchors Lm-1 and -2 to SC surfaces by binding to their LG domains and enables basement membrane (BM) assembly. Revealingly, non-BM-forming fibroblasts become competent for BM assembly when sulfatides are intercalated into their cell surfaces. Assembly is characterized by coalescence of sulfatide, DG, and c-Src into a Lm-associated complex; by DG-dependent recruitment of utrophin and Src activation; and by integrin-dependent focal adhesion kinase phosphorylation. Collectively, our findings suggest that sulfated glycolipids are key Lm anchors that determine which cell surfaces can assemble Lms to initiate BM assembly and DG- and integrin-mediated signaling.

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Sciatic nerve. (top three panels) Gal-sulfatide expression precedes that of Lm. Sections of rat embryos containing sciatic nerve (E14 and E17) or isolated sciatic nerve (P1–P7, adult) were immunostained with antibodies for gal-sulfatide (sulf, red) and Lm-2/4 (Lm2, green). Arrowheads indicate colocalizations of antibody immunofluorescence between paired panels, establishing the relationship at various points. (middle) Adult sciatic nerve was immunostained with antibodies for Lm-2/4, gal-sulfatide, neurofilament proteins (NFL160 or NFL200), and SC myelin basic protein (MBP), revealing the colocalization of gal-sulfatide to Lm and the polarized relationship to myelin and axon within nerve bundles. (bottom four panels) Expression of nuclear pSrc and pFAK in P7 nerve. Sections were stained with antibodies to β1-integrin (β1), αDG, c-Src-PY416 (pSrc), tyrosine-phosphorylated focal adhesion kinase (pFAK), and with DAPI.
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fig1: Sciatic nerve. (top three panels) Gal-sulfatide expression precedes that of Lm. Sections of rat embryos containing sciatic nerve (E14 and E17) or isolated sciatic nerve (P1–P7, adult) were immunostained with antibodies for gal-sulfatide (sulf, red) and Lm-2/4 (Lm2, green). Arrowheads indicate colocalizations of antibody immunofluorescence between paired panels, establishing the relationship at various points. (middle) Adult sciatic nerve was immunostained with antibodies for Lm-2/4, gal-sulfatide, neurofilament proteins (NFL160 or NFL200), and SC myelin basic protein (MBP), revealing the colocalization of gal-sulfatide to Lm and the polarized relationship to myelin and axon within nerve bundles. (bottom four panels) Expression of nuclear pSrc and pFAK in P7 nerve. Sections were stained with antibodies to β1-integrin (β1), αDG, c-Src-PY416 (pSrc), tyrosine-phosphorylated focal adhesion kinase (pFAK), and with DAPI.

Mentions: The order of expression of gal-sulfatide and Lms was evaluated in developing rat sciatic nerves (Fig. 1). Gal-sulfatide was detected as early as E14 in an intracellular and linear pattern in the absence of detectable γ1-Lm. By E17, extracellular α2/γ1-Lms colocalized with the gal-sulfatide in linear BM-like patterns that were more prominent by P1. In the adult nerve, most of the sulfatide was located on the outside BM zone of myelinated axons in a polarized fashion. Thus, sulfatide expression occurs before initiation of BM assembly.


Laminin-sulfatide binding initiates basement membrane assembly and enables receptor signaling in Schwann cells and fibroblasts.

Li S, Liquari P, McKee KK, Harrison D, Patel R, Lee S, Yurchenco PD - J. Cell Biol. (2005)

Sciatic nerve. (top three panels) Gal-sulfatide expression precedes that of Lm. Sections of rat embryos containing sciatic nerve (E14 and E17) or isolated sciatic nerve (P1–P7, adult) were immunostained with antibodies for gal-sulfatide (sulf, red) and Lm-2/4 (Lm2, green). Arrowheads indicate colocalizations of antibody immunofluorescence between paired panels, establishing the relationship at various points. (middle) Adult sciatic nerve was immunostained with antibodies for Lm-2/4, gal-sulfatide, neurofilament proteins (NFL160 or NFL200), and SC myelin basic protein (MBP), revealing the colocalization of gal-sulfatide to Lm and the polarized relationship to myelin and axon within nerve bundles. (bottom four panels) Expression of nuclear pSrc and pFAK in P7 nerve. Sections were stained with antibodies to β1-integrin (β1), αDG, c-Src-PY416 (pSrc), tyrosine-phosphorylated focal adhesion kinase (pFAK), and with DAPI.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2171891&req=5

fig1: Sciatic nerve. (top three panels) Gal-sulfatide expression precedes that of Lm. Sections of rat embryos containing sciatic nerve (E14 and E17) or isolated sciatic nerve (P1–P7, adult) were immunostained with antibodies for gal-sulfatide (sulf, red) and Lm-2/4 (Lm2, green). Arrowheads indicate colocalizations of antibody immunofluorescence between paired panels, establishing the relationship at various points. (middle) Adult sciatic nerve was immunostained with antibodies for Lm-2/4, gal-sulfatide, neurofilament proteins (NFL160 or NFL200), and SC myelin basic protein (MBP), revealing the colocalization of gal-sulfatide to Lm and the polarized relationship to myelin and axon within nerve bundles. (bottom four panels) Expression of nuclear pSrc and pFAK in P7 nerve. Sections were stained with antibodies to β1-integrin (β1), αDG, c-Src-PY416 (pSrc), tyrosine-phosphorylated focal adhesion kinase (pFAK), and with DAPI.
Mentions: The order of expression of gal-sulfatide and Lms was evaluated in developing rat sciatic nerves (Fig. 1). Gal-sulfatide was detected as early as E14 in an intracellular and linear pattern in the absence of detectable γ1-Lm. By E17, extracellular α2/γ1-Lms colocalized with the gal-sulfatide in linear BM-like patterns that were more prominent by P1. In the adult nerve, most of the sulfatide was located on the outside BM zone of myelinated axons in a polarized fashion. Thus, sulfatide expression occurs before initiation of BM assembly.

Bottom Line: This glycolipid anchors Lm-1 and -2 to SC surfaces by binding to their LG domains and enables basement membrane (BM) assembly.Revealingly, non-BM-forming fibroblasts become competent for BM assembly when sulfatides are intercalated into their cell surfaces.Collectively, our findings suggest that sulfated glycolipids are key Lm anchors that determine which cell surfaces can assemble Lms to initiate BM assembly and DG- and integrin-mediated signaling.

View Article: PubMed Central - PubMed

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

ABSTRACT
Endoneurial laminins (Lms), beta1-integrins, and dystroglycan (DG) are important for Schwann cell (SC) ensheathment and myelination of axons. We now show that SC expression of galactosyl-sulfatide, a Lm-binding glycolipid, precedes that of Lms in developing nerves. This glycolipid anchors Lm-1 and -2 to SC surfaces by binding to their LG domains and enables basement membrane (BM) assembly. Revealingly, non-BM-forming fibroblasts become competent for BM assembly when sulfatides are intercalated into their cell surfaces. Assembly is characterized by coalescence of sulfatide, DG, and c-Src into a Lm-associated complex; by DG-dependent recruitment of utrophin and Src activation; and by integrin-dependent focal adhesion kinase phosphorylation. Collectively, our findings suggest that sulfated glycolipids are key Lm anchors that determine which cell surfaces can assemble Lms to initiate BM assembly and DG- and integrin-mediated signaling.

Show MeSH
Related in: MedlinePlus