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Human melanoma TrkC: its association with a purine-analog-sensitive kinase activity
Dario Marchetti1, Brian Murry, Jennifer Galjour
1Department of Comparative Biomedical Sciences, SVM, Louisiana State University at Baton Rouge, Baton Rouge, Louisiana 70803, USA. dmarchetti@vetmed.lsu.edu
Abstract:
The various members of the Trk tyrosine kinase family and p75 neurotrophin receptor (p75(NTR)) have been identified as signaling receptors for the structurally related members of the neurotrophins (NT) family. We have previously reported that NT treatment of murine and human brain-metastatic melanoma cells affects their invasive capacities and increases the production of extracellular-matrix degradative enzymes. These cells express aberrant levels of functional p75(NTR) and TrkC, the putative high-affinity receptor for the neurotrophin NT-3. Here we demonstrate that, by using sensitive immune-complex kinase assays in human brain-metastatic (70W) melanoma cells, TrkC receptors associate with a kinase activity exhibiting a dose-dependent susceptibility to inhibition by the purine-analogs 6-thioguanine and 2-aminopurine. The activity of this purine-analog-sensitive kinase (PASK) was induced by NT-3 in a time-dependent fashion, phosphorylating exogenous myelin basic protein (MBP) but not denatured enolase. It is similar to the one reported to relate with p75(NTR) and TrkA receptors and stimulated by the prototypic NT, nerve growth factor. Thus, PASKs may represent unique signaling components common to NT receptors that could engage joint downstream signaling effectors in brain-metastatic melanoma.
Insights
Neurotrophin (NT) receptors like TrkC are linked to brain-metastatic melanoma. A purine-analog-sensitive kinase (PASK) activity associates with TrkC, suggesting a common signaling pathway for NT receptors in melanoma.
Area of Science:
- Neuro-oncology
- Molecular biology
- Cancer signaling
Background:
- Neurotrophins (NTs) and their receptors, Trk tyrosine kinases and p75 neurotrophin receptor (p75(NTR)), regulate cell functions.
- Previous studies showed NT treatment impacts melanoma cell invasion and extracellular matrix degradation.
- Brain-metastatic melanoma cells exhibit abnormal p75(NTR) and TrkC expression.
Purpose of the Study:
- To investigate the kinase activity associated with TrkC receptors in human brain-metastatic melanoma cells.
- To characterize the properties of this kinase activity and its response to neurotrophin-3 (NT-3).
Main Methods:
- Immune-complex kinase assays were performed on human brain-metastatic melanoma cells (70W).
- The kinase activity was assessed for its sensitivity to purine-analog inhibitors (6-thioguanine, 2-aminopurine).
- The effect of NT-3 on kinase activity and substrate phosphorylation (myelin basic protein) was evaluated.
Main Results:
- TrkC receptors were found to associate with a purine-analog-sensitive kinase (PASK).
- PASK activity was dose-dependently inhibited by 6-thioguanine and 2-aminopurine.
- NT-3 induced PASK activity in a time-dependent manner, phosphorylating myelin basic protein.
Conclusions:
- PASK activity is linked to TrkC receptors in brain-metastatic melanoma.
- This kinase activity is sensitive to purine analogs and induced by NT-3.
- PASK may represent a shared signaling component for neurotrophin receptors in melanoma, potentially influencing downstream effectors.