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HB-GAM (pleiotrophin) reverses inhibition of neural regeneration by the CNS extracellular matrix

View Article: PubMed Central - PubMed

ABSTRACT

Chondroitin sulfate (CS) glycosaminoglycans inhibit regeneration in the adult central nervous system (CNS). We report here that HB-GAM (heparin-binding growth-associated molecule; also known as pleiotrophin), a CS-binding protein expressed at high levels in the developing CNS, reverses the role of the CS chains in neurite growth of CNS neurons in vitro from inhibition to activation. The CS-bound HB-GAM promotes neurite growth through binding to the cell surface proteoglycan glypican-2; furthermore, HB-GAM abrogates the CS ligand binding to the inhibitory receptor PTPσ (protein tyrosine phosphatase sigma). Our in vivo studies using two-photon imaging of CNS injuries support the in vitro studies and show that HB-GAM increases dendrite regeneration in the adult cerebral cortex and axonal regeneration in the adult spinal cord. Our findings may enable the development of novel therapies for CNS injuries.

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HB-GAM-induced neurite outgrowth on aggrecan depends on the CS chains of the substrate-bound aggrecan and on the HS chains of the neuron surface glypican-2.(a,b,g) Neurite growth induced by aggrecan + soluble HB-GAM is blocked by the chondroitinase ABC (2 U/ml, 30 min) pretreatment of the aggrecan-coated substrate. (c,h) Neurite growth on the aggrecan + HB-GAM subsrate is blocked by heparinase III (0.017 U/ml) but not by heparinases I or II (0.017 U/ml). (d,i) Neurite growth induced by aggrecan + soluble HB-GAM is blocked by preincubation of cells with phospholipase C (PLC; 0.4 U/ml, 1 h). (e,f,j) Neurite growth on aggrecan in the presence of HB-GAM is inhibited by the glypican-2 (GPC2) siRNA. The scale bar in a (20 μm) is valid for a–f. Error bars represent standard error of mean (SEM), symbols *, ** and *** represent P < 0.05, 0.01 and 0.001, respectively. All data are based on 3 independent experiments.
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f3: HB-GAM-induced neurite outgrowth on aggrecan depends on the CS chains of the substrate-bound aggrecan and on the HS chains of the neuron surface glypican-2.(a,b,g) Neurite growth induced by aggrecan + soluble HB-GAM is blocked by the chondroitinase ABC (2 U/ml, 30 min) pretreatment of the aggrecan-coated substrate. (c,h) Neurite growth on the aggrecan + HB-GAM subsrate is blocked by heparinase III (0.017 U/ml) but not by heparinases I or II (0.017 U/ml). (d,i) Neurite growth induced by aggrecan + soluble HB-GAM is blocked by preincubation of cells with phospholipase C (PLC; 0.4 U/ml, 1 h). (e,f,j) Neurite growth on aggrecan in the presence of HB-GAM is inhibited by the glypican-2 (GPC2) siRNA. The scale bar in a (20 μm) is valid for a–f. Error bars represent standard error of mean (SEM), symbols *, ** and *** represent P < 0.05, 0.01 and 0.001, respectively. All data are based on 3 independent experiments.

Mentions: Another striking effect of chondroitinase ABC treatment was to abrogate the ability of aggrecan to enhance neurite outgrowth in the presence of soluble HB-GAM (Fig. 3a,b,g). These experiments show that the same CSPG can serve as an inhibitor of neurite outgrowth in the absence of HB-GAM or as an activator of neurite outgrowth in the presence of HB-GAM. The CS side chains of CSPGs are required to bind HB-GAM, and the resulting CSPG/HB-GAM substrate then induces neurite extension. This places HB-GAM as a pivotal factor to reverse the role of the CS chains in neurite outgrowth.


HB-GAM (pleiotrophin) reverses inhibition of neural regeneration by the CNS extracellular matrix
HB-GAM-induced neurite outgrowth on aggrecan depends on the CS chains of the substrate-bound aggrecan and on the HS chains of the neuron surface glypican-2.(a,b,g) Neurite growth induced by aggrecan + soluble HB-GAM is blocked by the chondroitinase ABC (2 U/ml, 30 min) pretreatment of the aggrecan-coated substrate. (c,h) Neurite growth on the aggrecan + HB-GAM subsrate is blocked by heparinase III (0.017 U/ml) but not by heparinases I or II (0.017 U/ml). (d,i) Neurite growth induced by aggrecan + soluble HB-GAM is blocked by preincubation of cells with phospholipase C (PLC; 0.4 U/ml, 1 h). (e,f,j) Neurite growth on aggrecan in the presence of HB-GAM is inhibited by the glypican-2 (GPC2) siRNA. The scale bar in a (20 μm) is valid for a–f. Error bars represent standard error of mean (SEM), symbols *, ** and *** represent P < 0.05, 0.01 and 0.001, respectively. All data are based on 3 independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5037378&req=5

f3: HB-GAM-induced neurite outgrowth on aggrecan depends on the CS chains of the substrate-bound aggrecan and on the HS chains of the neuron surface glypican-2.(a,b,g) Neurite growth induced by aggrecan + soluble HB-GAM is blocked by the chondroitinase ABC (2 U/ml, 30 min) pretreatment of the aggrecan-coated substrate. (c,h) Neurite growth on the aggrecan + HB-GAM subsrate is blocked by heparinase III (0.017 U/ml) but not by heparinases I or II (0.017 U/ml). (d,i) Neurite growth induced by aggrecan + soluble HB-GAM is blocked by preincubation of cells with phospholipase C (PLC; 0.4 U/ml, 1 h). (e,f,j) Neurite growth on aggrecan in the presence of HB-GAM is inhibited by the glypican-2 (GPC2) siRNA. The scale bar in a (20 μm) is valid for a–f. Error bars represent standard error of mean (SEM), symbols *, ** and *** represent P < 0.05, 0.01 and 0.001, respectively. All data are based on 3 independent experiments.
Mentions: Another striking effect of chondroitinase ABC treatment was to abrogate the ability of aggrecan to enhance neurite outgrowth in the presence of soluble HB-GAM (Fig. 3a,b,g). These experiments show that the same CSPG can serve as an inhibitor of neurite outgrowth in the absence of HB-GAM or as an activator of neurite outgrowth in the presence of HB-GAM. The CS side chains of CSPGs are required to bind HB-GAM, and the resulting CSPG/HB-GAM substrate then induces neurite extension. This places HB-GAM as a pivotal factor to reverse the role of the CS chains in neurite outgrowth.

View Article: PubMed Central - PubMed

ABSTRACT

Chondroitin sulfate (CS) glycosaminoglycans inhibit regeneration in the adult central nervous system (CNS). We report here that HB-GAM (heparin-binding growth-associated molecule; also known as pleiotrophin), a CS-binding protein expressed at high levels in the developing CNS, reverses the role of the CS chains in neurite growth of CNS neurons in vitro from inhibition to activation. The CS-bound HB-GAM promotes neurite growth through binding to the cell surface proteoglycan glypican-2; furthermore, HB-GAM abrogates the CS ligand binding to the inhibitory receptor PTP&sigma; (protein tyrosine phosphatase sigma). Our in vivo studies using two-photon imaging of CNS injuries support the in vitro studies and show that HB-GAM increases dendrite regeneration in the adult cerebral cortex and axonal regeneration in the adult spinal cord. Our findings may enable the development of novel therapies for CNS injuries.

No MeSH data available.


Related in: MedlinePlus