Neuroglycan C Is a Novel Midkine Receptor Involved in Process Elongation of Oligodendroglial Precursor-like Cells

Abstract

Midkine is a heparin-binding growth factor that promotes cell attachment and process extension in undifferentiated bipolar CG-4 cells, an oligodendroglial precursor cell line. We found that CG-4 cells expressed a non-proteoglycan form of neuroglycan C, known as a part-time transmembrane proteoglycan. We demonstrated that neuroglycan C before or after chondroitinase ABC treatment bound to a midkine affinity column. Neuroglycan C lacking chondroitin sulfate chains was eluted with 0.5 M NaCl as a major fraction from the column. We confirmed that CG-4 cells expressed two isoforms of neuroglycan C, I, and III, by isolating cDNA. Among three functional domains of the extracellular part of neuroglycan C, the chondroitin sulfate attachment domain and acidic amino acid cluster box domain showed affinity for midkine, but the epidermal growth factor domain did not. Furthermore, cell surface neuroglycan C could be cross-linked with soluble midkine. Process extension on midkine-coated dishes was inhibited by either a monoclonal antineuroglycan C antibody C1 or a glutathione S-transferase-neuroglycan C fusion protein. Finally, stable transfectants of B104 neuroblastoma cells overexpressing neuroglycan C-I or neuroglycan C-III attached to the midkine substrate, spread well, and gave rise to cytoskeletal changes. Based on these results, we conclude that neuroglycan C is a novel component of midkine receptors involved in process elongation. Midkine (MK),2 a heparin-binding growth factor, is strongly expressed at the mid-embryonic stage of development and is preferentially expressed in the kidney after birth (1, 2). MK is a 13-kDa protein with about 50% sequence identity to pleiotrophin (PTN), which is also called heparin-binding growth-associated molecule (3, 4). MK promotes neurite outgrowth and migration in neuronal cells isolated from the embryonic brain (5-7) and prevents apoptosis (8, 9). MK also promotes the migration of inflammatory leukocytes (10) and thereby plays a key role in the etiology of neointima formation (10), renal injury (11, 12), rheumatoid arthritis (13), and intraperitoneal adhesion after surgery (14). So far, protein-tyrosine phosphatase (7, 15), anaplastic lymphoma kinase (16), low density-lipoprotein receptor-related protein-1 (17), low density lipoprotein receptor-related protein 6 (9), and integrin ␣4␤1 and ␣6␤1 (18) have been identified as MK receptors. These molecules cooperate during MK signaling, possibly as a receptor complex (18). However, not all the molecules serving as MK receptors have been clarified. Importantly, we do not know whether a function specific to a class of cells such as neurite extension requires another receptor to transmit the specific signal or not. Here, we report that a cell surface molecule is specifically expressed in the nervous system as a component of the MK receptor in cells extending processes.When undifferentiated CG-4 cells, an oligodendrocyte precursor cell line, are cultured on dishes coated with MK or PTN, they quickly extend processes and adopt bipolar shapes ...

Midkine and Alk signaling in sympathetic neuron proliferation and neuroblastoma predisposition

“…However, besides Alk , a number of additional receptor types have been identified for Mk, including PTP (Maeda et al, 1999), integrins , Notch2 (Huang et al, 2008), LDL receptor-related protein (Muramatsu et al, 2000) and neuroglycan C (Ichihara-Tanaka et al, 2006). Both MK and PTN are expressed at high levels in neuroblastoma, but only MK expression correlates with aggressive NB (Fiegel et al, 2008;Nakagawara et al, 1995).…”

Neuroglycan C, A Brain-Specific Chondroitin Sulfate Proteoglycan, Interacts with Pleiotrophin, A Heparin-Binding Growth Factor

“…MK has been shown to bind to NGC [6]. Our results suggest that PTN is a ligand for NGC in the developing CNS.…”

“…2a). Ichihara-Tanaka et al [6] reported that NGC bound to midkine (MK), a heparinbinding growth factor with 45% homology to PTN. Therefore, using immunoblotting, we examined the possibility that some of these bands represented PTN and MK.…”

Functional Receptors and Intracellular Signal Pathways of Midkine (MK) and Pleiotrophin (PTN)

“…55) Both MK and PTN bind to the acidic amino cluster box domain of NGC without being affected by chondroitinase ABC treatment, while MK also binds to the chondroitin sulfate attachment domain, which is sensitive to chondroitinase ABC digestion. 56,57) Substrate coated with MK or PTN promotes cell attachment and process extension in the undifferentiated bipolar CG-4 cells, and this function can be inhibited by monoclonal anti-NGC antibody or a glutathione S-transferase-NGC fusion protein. 56,58) 3.5.…”

“…56,57) Substrate coated with MK or PTN promotes cell attachment and process extension in the undifferentiated bipolar CG-4 cells, and this function can be inhibited by monoclonal anti-NGC antibody or a glutathione S-transferase-NGC fusion protein. 56,58) 3.5. Low-Density Lipoprotein (LDL) Receptor Related Protein (LRP) LRP, belonging to the LDL receptor superfamily, is a large endocytic receptor that serves to internalize ligands into lysosome for degradation and metabolism.…”