Résumé :
|
Communication n° 359. Anaplastic lymphoma kinase (ALK) is a tyrosine kinase receptor whose transcript is transiently expressed in specific regions of the central and peripheral nervous systems during development and remains present at a low level in the adult nervous system. The nature of ALK ligand in vertebrate is controversial therefore we consider ALK as an orphan receptor. In order to localize the protein and to obtain potential ligands substitutes, we produced a panel of monoclonal antibodies (mAbs) directed against the extracellular domain of the human receptor. Some mAbs cross-reacting with the mouse and rat receptor allowed us to localize ALK in the nervous system. We are currently performing studies in the developing spinal chord, dorsal and ventral roots and also neuromuscular junctions. We previously showed that a constitutive active form of ALK induces the differentiation of the PC12 cells through the MAP kinase pathway (Souttou et al., 2001, JBC, 276, 9526). Therefore we used these cells to reveal potential mAb agonists. MAb 46 and mAb 48 were selected as inducing the neurite outgrowth of PC12 transiently expressing ALK in the nanomolar range. Treatment of HEK 293 cells stably expressing ALK with these mAbs leads to ALK phosphorylation and MAP kinase pathway activation as expected. Moreover we showed for the first time that ALK activation also resulted in a specific activation of STAT3. The STAT pathways having been involved in neuronal survival, ALK activation could contribute to this cellular effect. In the absence of clearly established ligand(s) in vertebrates, the availability of mAbs allowing the activation of ALK receptor will be useful to better understand its biological roles in the developing nervous system.
|