Heterogeneity of the chondroitin sulfate portion of phosphacan/6B4 proteoglycan regulates its binding affinity for pleiotrophin/heparin binding growth-associated molecule.
PTP zeta is a receptor-type protein-tyrosine phosphatase that is synthesized as a chondroitin sulfate proteoglycan and uses pleiotrophin as a ligand. The chondroitin sulfate portion of this receptor is essential for high affinity binding to pleiotrophin. Here, we purified phosphacan, which corresponds to the extracellular domain of PTP zeta, from postnatal day 7 (P7) and P12 rat cerebral cortex (PG-P7 and PG-P12, respectively) and from P20 rat whole brain (PG-P20). The chondroitin sulfate of these preparations displayed immunologically and compositionally different structures. In particular, only PG-P20 reacted with the monoclonal antibody MO-225, which recognizes chondroitin sulfate containing the GlcA(2S)beta 1-3GalNAc(6S) disaccharide unit (D unit). Analysis of the chondroitinase digestion products revealed that GlcA beta 1-3GalNAc(4S) disaccharide unit (A unit) was the major component in these preparations and that PG-P20 contained 1.3% D unit, which was not detected in PG-P7 and PG-P12. Interaction analysis using a surface plasmon resonance biosensor indicated that PG-P20 had approximately 5-fold stronger affinity for pleiotrophin (dissociation constant (KD) = 0.14 nM) than PG-P7 and PG-P12, although all these preparations showed similar low affinity binding to pleiotrophin after chondroitinase ABC digestion (KD = 1.4 approximately 1.6 nM). We also found that shark cartilage chondroitin sulfate D containing approximately 20% D unit bound to pleiotrophin with moderate affinity (KD = 2.7 nM), whereas whale cartilage chondroitin sulfate A showed no binding to this growth factor. These results suggest that variation of chondroitin sulfate plays important roles in the regulation of signal transduction in the brain.
Maeda
Nobuaki
N
Department of Developmental Neuroscience, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, Tokyo 183-8526. maedan@tmin.ac.jp
He
Jue
J
Yajima
Yuki
Y
Mikami
Tadahisa
T
Sugahara
Kazuyuki
K
Yabe
Tomio
T
D000375:Aging; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000254:growth & development*; D001923:Brain Chemistry; D002240:Carbohydrate Sequence; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002540:Cerebral Cortex / Q000737:chemistry; D011508:Chondroitin Sulfate Proteoglycans / Q000737:chemistry* / Q000378:metabolism; D002809:Chondroitin Sulfates / Q000737:chemistry* / Q000378:metabolism; D016207:Cytokines / Q000737:chemistry* / Q000378:metabolism; D004187:Disaccharides / Q000737:chemistry; D016220:Fibroblast Growth Factor 1 / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5; D011994:Recombinant Proteins / Q000737:chemistry; D020349:Surface Plasmon Resonance
D002352:Carrier Proteins; D011508:Chondroitin Sulfate Proteoglycans; D016207:Cytokines; D004187:Disaccharides; D011994:Recombinant Proteins; D016220:Fibroblast Growth Factor 1; C066845:pleiotrophin; D002809:Chondroitin Sulfates; C516895:PTPRZ1 protein, human; D017027:Protein Tyrosine Phosphatases; C516896:Ptprz1 protein, mouse; C516897:Ptprz1 protein, rat; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5