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Axonal neuregulin signals cells of the oligodendrocyte lineage through activation of HER4 and Schwann cells through HER2 and HER3.

Vartanian T, Goodearl A, Viehöver A, Fischbach G - J. Cell Biol. (1997)

Bottom Line: We have found that oligodendrocite-type II astrocyte (O2A) progenitor cells and mature oligodendrocytes express HER2 and HER4 but no HER3.Coimmunoprecipitation experiments indicate that receptor activation in Schwann cells results in the formation of HER2:HER3 heterodimers.The use of unique neuregulin receptor combinations in oligodendrocytes and Schwann cells likely results in recruitment of different signaling pathways and thus provides a basis for different biological responses.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.

ABSTRACT
We are interested in the signaling between axons and glia that leads to myelination and maintenance of the myelin internode, and we have focused on the role of neuregulins and their receptors. Neuregulins are a family of ligands that includes heregulin, neu differentiation factor, glial growth factor, and the acetylcholine receptor-inducing activity. Three signal transducing transmembrane receptors for neuregulins, which bear significant homology to the EGF receptor, are currently known: HER2 (erbB2), HER3 (erbB3), and HER4 (erbB4). We have found that oligodendrocite-type II astrocyte (O2A) progenitor cells and mature oligodendrocytes express HER2 and HER4 but no HER3. Schwann cells express HER2 and HER3 but little HER4. In O2A progenitor cells and oligodendrocytes, recombinant neuregulin induces the rapid tyrosine phosphorylation of only HER4. HER2 is not phosphorylated in cells of the oligodendrocyte lineage, but a physical interaction between HER2 and HER4 was detected in coimmunoprecipitation experiments. In Schwann cells, neuregulin induces the phosphorylation of both HER2 and HER3. Coimmunoprecipitation experiments indicate that receptor activation in Schwann cells results in the formation of HER2:HER3 heterodimers. Neuregulin localized immunocytochemically was present on neurites of cultured dorsal root ganglion neurons, and it was released into the medium in a form that promoted receptor tyrosine phosphorylation. Neuregulins therefore meet important criteria expected of molecules involved in axonal-glial signaling. The use of unique neuregulin receptor combinations in oligodendrocytes and Schwann cells likely results in recruitment of different signaling pathways and thus provides a basis for different biological responses.

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Neuregulin-induced tyrosine phosphorylation of HER4  in O2A progenitor cells and oligodendrocytes. (A) Cultures were  treated with 100 pM neuregulin (EGF-like β1 domain of neu differentiation factor) or control buffer (0.1% recrystalized BSA in  PBS) for 5 min, harvested, and HER4 or HER2 immunoprecipitated as described. All three panels represent autoradiographs of  the same membrane probed sequentially with three different  primary antibodies: monoclonal antiphosphotyrosine (upper),  polyclonal anti-HER2 (middle), and anti-HER4 (lower). Before  reprobing the membrane, primary and secondary antibody complexes were stripped as described in Materials and Methods. In  both O2A progenitor cells and oligodendrocytes, neuregulin induces the phosphorylation of a band at ∼180-kD that comigrates  with HER4 but not HER2. HER4 is seen in the HER2 immunoprecipitates regardless of neuregulin treatment, indicating an association of the two receptors in the absence of ligand. The bands  at ∼190 and 135 kD recognized by HER4 antibodies in HER4  immunoprecipitates (lower) are of unknown significance but may  represent unprocessed and truncated forms of the receptor. (B)  Time course of HER4 phosphorylation. Cultures of O2A progenitors were treated for the times indicated and HER4 was immunoprecipitated. Immunoprecipitates were treated as above using  monoclonal antiphosphotyrosine as the primary antibody, and  the autoradiograph is shown.
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Figure 3: Neuregulin-induced tyrosine phosphorylation of HER4 in O2A progenitor cells and oligodendrocytes. (A) Cultures were treated with 100 pM neuregulin (EGF-like β1 domain of neu differentiation factor) or control buffer (0.1% recrystalized BSA in PBS) for 5 min, harvested, and HER4 or HER2 immunoprecipitated as described. All three panels represent autoradiographs of the same membrane probed sequentially with three different primary antibodies: monoclonal antiphosphotyrosine (upper), polyclonal anti-HER2 (middle), and anti-HER4 (lower). Before reprobing the membrane, primary and secondary antibody complexes were stripped as described in Materials and Methods. In both O2A progenitor cells and oligodendrocytes, neuregulin induces the phosphorylation of a band at ∼180-kD that comigrates with HER4 but not HER2. HER4 is seen in the HER2 immunoprecipitates regardless of neuregulin treatment, indicating an association of the two receptors in the absence of ligand. The bands at ∼190 and 135 kD recognized by HER4 antibodies in HER4 immunoprecipitates (lower) are of unknown significance but may represent unprocessed and truncated forms of the receptor. (B) Time course of HER4 phosphorylation. Cultures of O2A progenitors were treated for the times indicated and HER4 was immunoprecipitated. Immunoprecipitates were treated as above using monoclonal antiphosphotyrosine as the primary antibody, and the autoradiograph is shown.

Mentions: Cells of the oligodendrocyte lineage express HER2 and HER4, and therefore HER2:HER2, HER4:HER4, and HER2:HER4 homo- and heterodimers are possible signal transducing receptor units. In transfected cell lines, data suggest that HER2:HER2 homodimers are not functional signal transducing units because they lack the ability to bind neuregulin. To investigate receptor usage in primary glial cells, we examined O2A progenitor cells and oligodendrocytes for the receptor tyrosine phosphorylation events after treatment with neuregulin. In the upper panel of Fig. 3 A, the tyrosine phosphorylation of an ∼180-kD protein is evident in HER4 and HER2 immunoprecipitates from both neuregulin-treated O2A progenitor cells and oligodendrocytes. HER2 and HER4 may be resolved by SDSPAGE with approximate molecular masses of 185 and 180 kD, respectively, and based on relative mobility of the two receptors, it appeared that the tyrosine-phosphorylated protein was HER4 rather than HER2. To definitively assign the tyrosine-phosphorylated protein to either HER2 or HER4, we stripped the membranes and reprobed them for either HER2 (Fig. 3 A, middle) or HER4 (Fig. 3 A, lower). Based on alignment of the resultant autoradiograms, it was clear that the tyrosine-phosphorylated band comigrated with HER4 and not HER2. Significant amounts of HER4 were present in HER2 immunoprecipitates in both ligand-treated and control cultures, but little HER2 was detected in HER4 immunoprecipitates. This suggested to us that HER2:HER4 heterodimers may exist in the presence and absence of ligand. Furthermore, the fact that HER4 is present in HER2 immunoprecipitates but not the converse suggests that HER4 is in excess of HER2 and that HER4 homodimers actually form. The definitive demonstration of HER4 homodimers will require chemical cross-linking studies.


Axonal neuregulin signals cells of the oligodendrocyte lineage through activation of HER4 and Schwann cells through HER2 and HER3.

Vartanian T, Goodearl A, Viehöver A, Fischbach G - J. Cell Biol. (1997)

Neuregulin-induced tyrosine phosphorylation of HER4  in O2A progenitor cells and oligodendrocytes. (A) Cultures were  treated with 100 pM neuregulin (EGF-like β1 domain of neu differentiation factor) or control buffer (0.1% recrystalized BSA in  PBS) for 5 min, harvested, and HER4 or HER2 immunoprecipitated as described. All three panels represent autoradiographs of  the same membrane probed sequentially with three different  primary antibodies: monoclonal antiphosphotyrosine (upper),  polyclonal anti-HER2 (middle), and anti-HER4 (lower). Before  reprobing the membrane, primary and secondary antibody complexes were stripped as described in Materials and Methods. In  both O2A progenitor cells and oligodendrocytes, neuregulin induces the phosphorylation of a band at ∼180-kD that comigrates  with HER4 but not HER2. HER4 is seen in the HER2 immunoprecipitates regardless of neuregulin treatment, indicating an association of the two receptors in the absence of ligand. The bands  at ∼190 and 135 kD recognized by HER4 antibodies in HER4  immunoprecipitates (lower) are of unknown significance but may  represent unprocessed and truncated forms of the receptor. (B)  Time course of HER4 phosphorylation. Cultures of O2A progenitors were treated for the times indicated and HER4 was immunoprecipitated. Immunoprecipitates were treated as above using  monoclonal antiphosphotyrosine as the primary antibody, and  the autoradiograph is shown.
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Related In: Results  -  Collection

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Figure 3: Neuregulin-induced tyrosine phosphorylation of HER4 in O2A progenitor cells and oligodendrocytes. (A) Cultures were treated with 100 pM neuregulin (EGF-like β1 domain of neu differentiation factor) or control buffer (0.1% recrystalized BSA in PBS) for 5 min, harvested, and HER4 or HER2 immunoprecipitated as described. All three panels represent autoradiographs of the same membrane probed sequentially with three different primary antibodies: monoclonal antiphosphotyrosine (upper), polyclonal anti-HER2 (middle), and anti-HER4 (lower). Before reprobing the membrane, primary and secondary antibody complexes were stripped as described in Materials and Methods. In both O2A progenitor cells and oligodendrocytes, neuregulin induces the phosphorylation of a band at ∼180-kD that comigrates with HER4 but not HER2. HER4 is seen in the HER2 immunoprecipitates regardless of neuregulin treatment, indicating an association of the two receptors in the absence of ligand. The bands at ∼190 and 135 kD recognized by HER4 antibodies in HER4 immunoprecipitates (lower) are of unknown significance but may represent unprocessed and truncated forms of the receptor. (B) Time course of HER4 phosphorylation. Cultures of O2A progenitors were treated for the times indicated and HER4 was immunoprecipitated. Immunoprecipitates were treated as above using monoclonal antiphosphotyrosine as the primary antibody, and the autoradiograph is shown.
Mentions: Cells of the oligodendrocyte lineage express HER2 and HER4, and therefore HER2:HER2, HER4:HER4, and HER2:HER4 homo- and heterodimers are possible signal transducing receptor units. In transfected cell lines, data suggest that HER2:HER2 homodimers are not functional signal transducing units because they lack the ability to bind neuregulin. To investigate receptor usage in primary glial cells, we examined O2A progenitor cells and oligodendrocytes for the receptor tyrosine phosphorylation events after treatment with neuregulin. In the upper panel of Fig. 3 A, the tyrosine phosphorylation of an ∼180-kD protein is evident in HER4 and HER2 immunoprecipitates from both neuregulin-treated O2A progenitor cells and oligodendrocytes. HER2 and HER4 may be resolved by SDSPAGE with approximate molecular masses of 185 and 180 kD, respectively, and based on relative mobility of the two receptors, it appeared that the tyrosine-phosphorylated protein was HER4 rather than HER2. To definitively assign the tyrosine-phosphorylated protein to either HER2 or HER4, we stripped the membranes and reprobed them for either HER2 (Fig. 3 A, middle) or HER4 (Fig. 3 A, lower). Based on alignment of the resultant autoradiograms, it was clear that the tyrosine-phosphorylated band comigrated with HER4 and not HER2. Significant amounts of HER4 were present in HER2 immunoprecipitates in both ligand-treated and control cultures, but little HER2 was detected in HER4 immunoprecipitates. This suggested to us that HER2:HER4 heterodimers may exist in the presence and absence of ligand. Furthermore, the fact that HER4 is present in HER2 immunoprecipitates but not the converse suggests that HER4 is in excess of HER2 and that HER4 homodimers actually form. The definitive demonstration of HER4 homodimers will require chemical cross-linking studies.

Bottom Line: We have found that oligodendrocite-type II astrocyte (O2A) progenitor cells and mature oligodendrocytes express HER2 and HER4 but no HER3.Coimmunoprecipitation experiments indicate that receptor activation in Schwann cells results in the formation of HER2:HER3 heterodimers.The use of unique neuregulin receptor combinations in oligodendrocytes and Schwann cells likely results in recruitment of different signaling pathways and thus provides a basis for different biological responses.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.

ABSTRACT
We are interested in the signaling between axons and glia that leads to myelination and maintenance of the myelin internode, and we have focused on the role of neuregulins and their receptors. Neuregulins are a family of ligands that includes heregulin, neu differentiation factor, glial growth factor, and the acetylcholine receptor-inducing activity. Three signal transducing transmembrane receptors for neuregulins, which bear significant homology to the EGF receptor, are currently known: HER2 (erbB2), HER3 (erbB3), and HER4 (erbB4). We have found that oligodendrocite-type II astrocyte (O2A) progenitor cells and mature oligodendrocytes express HER2 and HER4 but no HER3. Schwann cells express HER2 and HER3 but little HER4. In O2A progenitor cells and oligodendrocytes, recombinant neuregulin induces the rapid tyrosine phosphorylation of only HER4. HER2 is not phosphorylated in cells of the oligodendrocyte lineage, but a physical interaction between HER2 and HER4 was detected in coimmunoprecipitation experiments. In Schwann cells, neuregulin induces the phosphorylation of both HER2 and HER3. Coimmunoprecipitation experiments indicate that receptor activation in Schwann cells results in the formation of HER2:HER3 heterodimers. Neuregulin localized immunocytochemically was present on neurites of cultured dorsal root ganglion neurons, and it was released into the medium in a form that promoted receptor tyrosine phosphorylation. Neuregulins therefore meet important criteria expected of molecules involved in axonal-glial signaling. The use of unique neuregulin receptor combinations in oligodendrocytes and Schwann cells likely results in recruitment of different signaling pathways and thus provides a basis for different biological responses.

Show MeSH
Related in: MedlinePlus