A ligand-inducible anaplastic lymphoma kinase chimera is endocytosis impaired
Michela Serresi1, Gina Piccinini, Elisa Pierpaoli
1Laboratory of Cellular and Molecular Biology, Institute of Clinical Medicine, University of Ancona, Via Tronto 10/A, 60020 Ancona, Italy.
Abstract:
Ligand-induced membrane trafficking of the anaplastic lymphoma kinase (ALK) was studied using a chimeric receptor in which the extracellular and transmembrane domain of ALK was substituted for the corresponding regions of epidermal growth factor receptor (EGFR). Wild-type EGFR, EGFR/ALK and an EGFR/ALK kinase negative mutant were independently expressed in mouse NR6 fibroblasts. The capacity of EGFR/ALK to mediate [125I]-EGF internalization, receptor degradation and downregulation, which has never been previously described, was assayed. The rate of [125I]-EGF-induced internalization mediated by the cytoplasmic domain of ALK was reduced several fold compared with the wild-type EGFR. The low rate of EGF internalization promoted by EGFR/ALK correlated with an impaired degradation and downregulation of the receptor and indicate that ALK is not subject to traditional mechanisms used to regulate receptor tyrosine kinase function. Accordingly, ALK-activated intracellular domain does not associate in vivo with c-cbl and does not undergo ligand-mediated ubiquitination. The current study provides new insight into the function and regulation of ALK suggesting that the relative long membrane residence of activated ALK might confers a more potent and prolonged signaling activity. Indeed NR6-EGFR/ALK cells exhibited a approximately 3-fold increase in a maximal mitogenic response than NR6-EGFR.
Insights
Anaplastic lymphoma kinase (ALK) shows slower internalization and degradation than epidermal growth factor receptor (EGFR). This prolonged membrane presence may enhance ALK
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Receptor tyrosine kinases (RTKs) like EGFR regulate cellular processes through ligand-induced internalization, degradation, and downregulation.
- The anaplastic lymphoma kinase (ALK) is implicated in cancer, but its membrane trafficking and regulation are not fully understood.
Purpose of the Study:
- To investigate the ligand-induced membrane trafficking and regulation of anaplastic lymphoma kinase (ALK).
- To compare the internalization, degradation, and downregulation of a chimeric EGFR/ALK receptor with wild-type EGFR.
Main Methods:
- A chimeric receptor (EGFR/ALK) was constructed by replacing EGFR's extracellular and transmembrane domains with those of ALK.
- This chimeric receptor and wild-type EGFR were expressed in mouse NR6 fibroblasts.
- The internalization rate of [125I]-EGF, receptor degradation, and downregulation were measured.
Main Results:
- EGFR/ALK mediated [125I]-EGF internalization at a significantly lower rate compared to wild-type EGFR.
- The impaired internalization of EGFR/ALK correlated with reduced receptor degradation and downregulation.
- ALK's intracellular domain did not associate with c-cbl or undergo ligand-mediated ubiquitination in vivo.
Conclusions:
- Anaplastic lymphoma kinase (ALK) is not regulated by traditional receptor tyrosine kinase mechanisms.
- The reduced internalization and impaired degradation suggest a longer membrane residence time for activated ALK.
- This prolonged signaling may contribute to a more potent and sustained mitogenic response.
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