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A Goodearl

Publications and source records attributed to A Goodearl.

5 recordsLinked to original sources
PubMed2000

Isolation and characterization of the notch ligand delta4.

Notch signaling plays a critical role in a variety of developmental programs. In vertebrates, the complexity of the process is underscored by the existence of multiple Notch receptors and multiple ligands, each of which displays a distinct expression profile. Furthermore, the ligands can be subdivided into two families, the Serrate/Jagged family and the Delta family. Here we present the isolation of a novel Notch ligand, Delta4. Expression analyses indicate that mouse Delta4 is highly expressed in the eye and lung during embryogenesis and in the heart, lung, liver, and kidney of the adult. Functionally, Delta4 is indistinguishable from Jagged1 in its abilities to inhibit myogenesis and to stimulate transcription through Notch1 and the DNA binding protein CSL.

3T3 Cells↗
PubMed2000

Cloning, characterization, and functional studies of human and mouse glycoprotein VI: a platelet-specific collagen receptor from the immunoglobulin superfamily.

Injuries to the vessel wall and subsequent exposure of collagen from the subendothelial matrix result in thrombus formation. In physiological conditions, the platelet plug limits blood loss. However, in pathologic conditions, such as rupture of atherosclerotic plaques, platelet-collagen interactions are associated with cardiovascular and cerebral vascular diseases. Platelet glycoprotein VI (GPVI) plays a crucial role in collagen-induced activation and aggregation of platelets, and people who are deficient in GPVI suffer from bleeding disorders. Based on the fact that GPVI is coupled to the Fc receptor (FcR)-gamma chain and thus should share homology with the FcR chains, the genes encoding human and mouse GPVI were identified. They belong to the immunoglobulin (Ig) superfamily and share 64% homology at the protein level. Functional evidence demonstrating the identity of the recombinant protein with GPVI was shown by binding to its natural ligand collagen; binding to convulxin (Cvx), a GPVI-specific ligand from snake venom; binding of anti-GPVI IgG isolated from a patient; and association to the FcR-gamma chain. The study also demonstrated that the soluble protein blocks Cvx and collagen-induced platelet aggregation and that GPVI expression is restricted to megakaryocytes and platelets. Finally, human GPVI was mapped to chromosome 19, long arm, region 1, band 3 (19q13), in the same region as multiple members of the Ig superfamily. This work offers the opportunity to explore the involvement of GPVI in thrombotic disease, to develop alternative antithrombotic compounds, and to characterize the mechanism involved in GPVI genetic deficiencies. (Blood. 2000;96:1798-1807)

Amino Acid Sequence↗
PubMed2000

Neuregulin induces the rapid association of focal adhesion kinase with the erbB2-erbB3 receptor complex in schwann cells.

Neuregulins signal cells by binding to an activating hetero- and homodimeric forms of the neuregulin receptors HER2 (erbB2), HER3 (erbB3), and HER4 (erbB4). Axonally derived neuregulin signals myelin forming cells of the central and peripheral nervous systems through different receptor complexes: oligodendrocytes through erbB2/erbB4 heterodimers and Schwann cells through erbB2/erbB3 heterodimers. Since the leading edge of myelinating cells interacts directly with the axonal surface, we were interested in determining if signaling molecules localized at the leading edge associate with activated neuregulin receptors. We found a novel association between neuregulin receptors and focal adhesion kinase (FAK) in primary cultures of Schwann cells. Following stimulation with ligand, maximal binding of FAK to HER2 occurred by 1 min whereas maximal binding to HER3 was delayed to approximately 7 min. FAK is localized in focal adhesions of Schwann cells. We have previously shown HER2 and HER3 are distributed evenly throughout the plasmalemma. Neuregulins thus use FAK to transmit intracellular signals and the differential kinetics of FAK association with individual neuregulin receptors, as well as its restricted subcellular localization, may play a role in specifying biologic responses.

Adaptor Proteins, Signal Transducing↗
PubMed1997

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

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.

Animals↗