title: Stress-induced switch in Numb isoforms enhances Notch-dependent expression of subtype-specific transient receptor potential channel.
abstract: The Notch signaling pathway plays an essential role in the regulation of cell specification by controlling differentiation, proliferation, and apoptosis. Numb is an intrinsic regulator of the Notch pathway and exists in four alternative splice variants that differ in the length of their phosphotyrosine-binding domain (PTB) and proline-rich region domains. The physiological relevance of the existence of the Numb splice variants and their exact regulation are still poorly understood. We previously reported that Numb switches from isoforms containing the insertion in PTB to isoforms lacking this insertion in neuronal cells subjected to trophic factor withdrawal (TFW). The functional relevance of the TFW-induced switch in Numb isoforms is not known. Here we provide evidence that the TFW-induced switch in Numb isoforms regulates Notch signaling strength and Notch target gene expression. PC12 cells stably overexpressing Numb isoforms lacking the PTB insertion exhibited higher basal Notch activity and Notch-dependent transcription of the transient receptor potential channel 6 (TRPC6) when compared with those overexpressing Numb isoforms with the PTB insertion. The differential regulation of TRPC6 expression is correlated with perturbed calcium signaling and increased neuronal vulnerability to TFW-induced death. Pharmacological inhibition of the Notch pathway or knockdown of TRPC6 function ameliorates the adverse effects caused by the TFW-induced switch in Numb isoforms. Taken together, our results indicate that Notch and Numb interaction may influence the sensitivity of neuronal cells to injurious stimuli by modulating calcium-dependent apoptotic signaling cascades.
authors.affiliation: Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32816, USA.
authors.forename: George A
authors.initials: GA
authors.lastname: Kyriazis
authors.forename: Cherine
authors.initials: C
authors.lastname: Belal
authors.forename: Meenu
authors.initials: M
authors.lastname: Madan
authors.forename: David G
authors.initials: DG
authors.lastname: Taylor
authors.forename: Jang
authors.initials: J
authors.lastname: Wang
authors.forename: Zelan
authors.initials: Z
authors.lastname: Wei
authors.forename: Jogi V
authors.initials: JV
authors.lastname: Pattisapu
authors.forename: Sic L
authors.initials: SL
authors.lastname: Chan
mesh_terms: D000818:Animals; D020013:Calcium Signaling; D016923:Cell Death; D006801:Humans; D008565:Membrane Proteins / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000502:physiology*; D009474:Neurons / Q000378:metabolism; D016716:PC12 Cells; D020033:Protein Isoforms; D051381:Rats; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction; D013312:Stress, Physiological; D050052:TRPC Cation Channels / Q000235:genetics*; D015854:Up-Regulation / Q000235:genetics
chemical_list: D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C113026:NUMB protein, human; D020033:Protein Isoforms; D051880:Receptors, Notch; D050052:TRPC Cation Channels; C492145:Trpc6 protein, rat