Direct binding of polysialic acid to a brain-derived neurotrophic factor depends on the degree of polymerization

Abstract

Polysialic acid (polySia) is the homopolymer of sialic acid and negatively regulates neuronal cell-cell and cell-extracellular matrix interactions through steric and repulsive hindrance due to its bulky polyanionic structure. Whether polySia also functions as a positive regulator in the nervous system through binding to specific ligands is not known. In the present study, we demonstrated that a brain-derived neurotrophic factor (BDNF) dimer binds directly to polySia to form a large complex with an M(r) greater than 2000 kDa under physiologic conditions. Although somewhat affected by the linkage and type of sialic acid components in the polySia, the complex formation is highly dependent on the polySia chain length. The minimum degree of polymerization required for the complex formation is 12. This is the first study to demonstrate the biologic significance of the degree of polySia polymerization in eukaryotes. Similar large polySia complexes form with other neurotrophic factors such as nerve growth factor, neurotrophin-3, and neurotrophin-4. Furthermore, the BDNF, after making a complex with polySia, can bind to the BDNF receptors, TrkB and p75NTR. The complex formation of BDNF with polySia upregulates growth or/and survival of neuroblastoma cells. These findings suggest that polySia functions as a reservoir of BDNF and other neurotrophic factors and may serve to regulate their local concentrations on the cell surface.

Functional Role of the Interaction between Polysialic Acid and Myristoylated Alanine-rich C Kinase Substrate at the Plasma Membrane

“…So far only brain-derived neurotrophic factor (8), histone H1 (9), and fibroblast growth factor 2 (10) have been identified as PSA-binding proteins and shown to directly interact with PSA. Here, we identified MARCKS as a novel interaction partner of PSA using an anti-idiotype approach.…”

Sialidase NEU4 Hydrolyzes Polysialic Acids of Neural Cell Adhesion Molecules and Negatively Regulates Neurite Formation by Hippocampal Neurons

“…Human neuroblastoma NB-1 cells (HSRRB, Osaka, Japan) were grown in 45% RPMI 1640 and 45% Eagle's medium with 10% heat-inactivated fatal bovine serum. Sialyloligomers with a degree of polymerization of 2 (DP2) and DP6 were obtained from Nacalai Tesque, (Kyoto, Japan), and DP18 oligomers were prepared as described previously (4). Antibodies were obtained from the following sources: anti-polySia (12F8) and anti-NCAM (N-CAM 13) and anti-calnexin (37/ calnexin) from BD Bioscience (San Jose, CA), anti-polySia (2-2B) from Chemicon International (Hants, UK), anti-NCAM (H-300) and anti-Lamp-1 (C-20) from Santa Cruz Biotechnology (Santa Cruz, CA), anti-FLAG (M2) and (FLA-1) from Sigma and MBL (Nagoya, Japan), respectively, anti-58K Golgi protein from Abcam (Cambridge, MA), and anti-TUJ1 (1-15-79) from Covance (Princeton, NJ).…”

“…Because of its polyanionic structure and large hydrated volume (2,3), modulation of polySia levels influences a wide range of structural changes in cell position and shape in the nervous system. Numerous studies have provided evidence for crucial functions of polySia on NCAM (4,5), especially with observation of NCAM and/or polysialyltransferase-deficient mice (6 -10). In fact, polySia has been implicated in synaptic plasticity, neuronal differentiation, and cell migration (1,11,12).…”

New Functions of Polysialic Acid and Its Relationship to Schizophrenia

“…In addition, we are analyzing the releasing mechanism of polySia. In this section, we will introduce brainderived neurotrophic factor (BDNF) (32,33), catecholamines (dopamine) (34,35), and a growth factor (FGF2) (36) as polySia-interacting molecules. D-1.…”

“…In addition, in the course of development and improvement of detection methods for polySia, several new polySia-containing glycoproteins have been discovered. The application of these detection methods to the study of polySia-related interactions (32,34,35) has revealed novel functions of polySia. In this mini-review, we will introduce the newly discovered functions of polySia and discuss the relationships between polySia and psychiatric disorders, particularly schizophrenia, which have been reported to date.…”