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PTP mu-dependent growth cone rearrangement is regulated by Cdc42
Jullia A Rosdahl1, Sonya E Ensslen, Jared A Niedenthal
1Department of Molecular and Microbiology, Case Western Reserve University, School of Medicine, 10900 Euclid Ave., Cleveland, Ohio 44106-4960,USA.
Abstract:
PTP mu is expressed in the developing nervous system and promotes growth and guidance of chick retinal ganglion cells. Using a newly developed growth cone rearrangement assay, we examined whether the small G-proteins were involved in PTP mu-dependent signaling. The stimulation of retinal cultures with purified PTP mu resulted in a striking morphological change in the growth cone, which becomes dominated by filopodia within 5 min of addition. This rearrangement in response to PTP mu stimulation was mediated by homophilic binding. We perturbed GTPase signaling using Toxin B, which inhibits Cdc42, Rac, and Rho, as well as the toxin Exoenzyme C3 that inhibits Rho. The PTP mu-induced growth cone rearrangement was blocked by Toxin B, but not by Exoenzyme C3. This result suggests that either Cdc42 or Rac are required but not Rho. To determine which GTPase was involved in PTP mu signaling, we utilized dominant-negative mutants of Cdc42 and Rac. Dominant-negative Cdc42 blocked PTP mu-induced rearrangement, while wild-type Cdc42 and dominant-negative Rac did not. Together, these results suggest a molecular signaling cascade beginning with PTP mu homophilic binding at the plasma membrane and the activation of Cdc42, which acts on the actin cytoskeleton to result in rearrangement of the growth cone.
Insights
Protein tyrosine phosphatase mu (PTP mu) signaling in developing neurons involves Cdc42 activation, leading to growth cone rearrangement. This pathway is crucial for neural development and cell guidance.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Signaling
Background:
- Protein tyrosine phosphatase mu (PTP mu) is expressed in the developing nervous system.
- PTP mu plays a role in promoting growth and guidance of chick retinal ganglion cells.
Purpose of the Study:
- To investigate the involvement of small G-proteins in PTP mu-dependent signaling.
- To elucidate the molecular mechanisms underlying PTP mu-mediated growth cone rearrangement.
Main Methods:
- Utilized a novel growth cone rearrangement assay.
- Stimulated retinal cultures with purified PTP mu.
- Perturbed GTPase signaling using Toxin B (inhibits Cdc42, Rac, Rho) and Exoenzyme C3 (inhibits Rho).
- Employed dominant-negative mutants of Cdc42 and Rac.
Main Results:
- PTP mu stimulation induced rapid growth cone morphological changes, dominated by filopodia.
- PTP mu-induced rearrangement was mediated by homophilic binding.
- Toxin B blocked the rearrangement, while Exoenzyme C3 did not, implicating Cdc42 or Rac.
- Dominant-negative Cdc42 inhibited rearrangement, whereas dominant-negative Rac did not.
Conclusions:
- PTP mu homophilic binding activates Cdc42.
- Activated Cdc42 acts on the actin cytoskeleton.
- This cascade results in the rearrangement of the neuronal growth cone.