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CRYP-2/cPTPRO is a neurite inhibitory repulsive guidance cue for retinal neurons in vitro.

Stepanek L, Sun QL, Wang J, Wang C, Bixby JL - J. Cell Biol. (2001)

Bottom Line: We found that the extracellular domain of cPTPRO is an antiadhesive, neurite inhibitory molecule for retinal neurons.This chemorepulsive effect could be regulated by the level of cGMP in the growth cone.Immunohistochemical examination of the retina indicated that cPTPRO has at least one heterophilic binding partner in the retina.

View Article: PubMed Central - PubMed

Affiliation: Neuroscience Program, University of Miami School of Medicine, Miami, FL 33136, USA.

ABSTRACT
Receptor protein tyrosine phosphatases (RPTPs) are implicated as regulators of axon growth and guidance. Genetic deletions in the fly have shown that type III RPTPs are important in axon pathfinding, but nothing is known about their function on a cellular level. Previous experiments in our lab have identified a type III RPTP, CRYP-2/cPTPRO, specifically expressed during the period of axon outgrowth in the chick brain; cPTPRO is expressed in the axons and growth cones of retinal and tectal projection neurons. We constructed a fusion protein containing the extracellular domain of cPTPRO fused to the Fc portion of mouse immunoglobulin G-1, and used it to perform in vitro functional assays. We found that the extracellular domain of cPTPRO is an antiadhesive, neurite inhibitory molecule for retinal neurons. In addition, cPTPRO had potent growth cone collapsing activity in vitro, and locally applied gradients of cPTPRO repelled growing retinal axons. This chemorepulsive effect could be regulated by the level of cGMP in the growth cone. Immunohistochemical examination of the retina indicated that cPTPRO has at least one heterophilic binding partner in the retina. Taken together, our results indicate that cPTPRO may act as a guidance cue for retinal ganglion cells during vertebrate development.

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cPTPRO inhibits neurite outgrowth on several growth-promoting substrates. Neurite growth was pronounced on 2-μl spots of 100 μg/ml rat tail collagen I (A), 20 μg/ml fibronectin (C), and 20 μg/ml N-cadherin–Fc (E). In contrast, when 100 μg/ml cPTPRO–Fc was mixed with collagen, fibronectin, or N-cadherin–Fc, neurite outgrowth was noticeably reduced (B, D, and F, respectively). Bar, 100 μm.
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fig6: cPTPRO inhibits neurite outgrowth on several growth-promoting substrates. Neurite growth was pronounced on 2-μl spots of 100 μg/ml rat tail collagen I (A), 20 μg/ml fibronectin (C), and 20 μg/ml N-cadherin–Fc (E). In contrast, when 100 μg/ml cPTPRO–Fc was mixed with collagen, fibronectin, or N-cadherin–Fc, neurite outgrowth was noticeably reduced (B, D, and F, respectively). Bar, 100 μm.

Mentions: The inhibitory effect of cPTPRO on retinal neurite growth could also be demonstrated for growth induced by proteins other than LN. Several other extracellular matrix proteins, including collagen I and fibronectin, also promote neurite growth from retinal neurons. We found that the cPTPRO ECD was inhibitory to neurite growth induced by either of these two proteins (Fig. 6 , A–D). Further, the ability of cPTPRO to inhibit neurite growth was not limited to extracellular matrix inducers, as cPTPRO also strongly inhibited neurite growth induced in retinal neurons by N-cadherin (Fig. 6, E and F). Quantification of neurite growth data demonstrated that cPTPRO inhibition of neurite growth was statistically significant when either the percentage of neurons with neurites (Fig. 7, C–E) or the length of individual neurites (unpublished data) was considered. The ability of cPTPRO to inhibit neurite growth induced by this variety of substrate proteins suggests that the effects are not due to binding of cPTPRO to the inducing protein, or by binding of cPTPRO to the neuronal receptors for these inducers. Rather, the data suggest that cPTPRO delivers an inhibitory signal to the cell by interacting with its own receptor.


CRYP-2/cPTPRO is a neurite inhibitory repulsive guidance cue for retinal neurons in vitro.

Stepanek L, Sun QL, Wang J, Wang C, Bixby JL - J. Cell Biol. (2001)

cPTPRO inhibits neurite outgrowth on several growth-promoting substrates. Neurite growth was pronounced on 2-μl spots of 100 μg/ml rat tail collagen I (A), 20 μg/ml fibronectin (C), and 20 μg/ml N-cadherin–Fc (E). In contrast, when 100 μg/ml cPTPRO–Fc was mixed with collagen, fibronectin, or N-cadherin–Fc, neurite outgrowth was noticeably reduced (B, D, and F, respectively). Bar, 100 μm.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196468&req=5

fig6: cPTPRO inhibits neurite outgrowth on several growth-promoting substrates. Neurite growth was pronounced on 2-μl spots of 100 μg/ml rat tail collagen I (A), 20 μg/ml fibronectin (C), and 20 μg/ml N-cadherin–Fc (E). In contrast, when 100 μg/ml cPTPRO–Fc was mixed with collagen, fibronectin, or N-cadherin–Fc, neurite outgrowth was noticeably reduced (B, D, and F, respectively). Bar, 100 μm.
Mentions: The inhibitory effect of cPTPRO on retinal neurite growth could also be demonstrated for growth induced by proteins other than LN. Several other extracellular matrix proteins, including collagen I and fibronectin, also promote neurite growth from retinal neurons. We found that the cPTPRO ECD was inhibitory to neurite growth induced by either of these two proteins (Fig. 6 , A–D). Further, the ability of cPTPRO to inhibit neurite growth was not limited to extracellular matrix inducers, as cPTPRO also strongly inhibited neurite growth induced in retinal neurons by N-cadherin (Fig. 6, E and F). Quantification of neurite growth data demonstrated that cPTPRO inhibition of neurite growth was statistically significant when either the percentage of neurons with neurites (Fig. 7, C–E) or the length of individual neurites (unpublished data) was considered. The ability of cPTPRO to inhibit neurite growth induced by this variety of substrate proteins suggests that the effects are not due to binding of cPTPRO to the inducing protein, or by binding of cPTPRO to the neuronal receptors for these inducers. Rather, the data suggest that cPTPRO delivers an inhibitory signal to the cell by interacting with its own receptor.

Bottom Line: We found that the extracellular domain of cPTPRO is an antiadhesive, neurite inhibitory molecule for retinal neurons.This chemorepulsive effect could be regulated by the level of cGMP in the growth cone.Immunohistochemical examination of the retina indicated that cPTPRO has at least one heterophilic binding partner in the retina.

View Article: PubMed Central - PubMed

Affiliation: Neuroscience Program, University of Miami School of Medicine, Miami, FL 33136, USA.

ABSTRACT
Receptor protein tyrosine phosphatases (RPTPs) are implicated as regulators of axon growth and guidance. Genetic deletions in the fly have shown that type III RPTPs are important in axon pathfinding, but nothing is known about their function on a cellular level. Previous experiments in our lab have identified a type III RPTP, CRYP-2/cPTPRO, specifically expressed during the period of axon outgrowth in the chick brain; cPTPRO is expressed in the axons and growth cones of retinal and tectal projection neurons. We constructed a fusion protein containing the extracellular domain of cPTPRO fused to the Fc portion of mouse immunoglobulin G-1, and used it to perform in vitro functional assays. We found that the extracellular domain of cPTPRO is an antiadhesive, neurite inhibitory molecule for retinal neurons. In addition, cPTPRO had potent growth cone collapsing activity in vitro, and locally applied gradients of cPTPRO repelled growing retinal axons. This chemorepulsive effect could be regulated by the level of cGMP in the growth cone. Immunohistochemical examination of the retina indicated that cPTPRO has at least one heterophilic binding partner in the retina. Taken together, our results indicate that cPTPRO may act as a guidance cue for retinal ganglion cells during vertebrate development.

Show MeSH
Related in: MedlinePlus