Tctex1 plays a key role in the α-synuclein autophagy lysosomal degradation pathway

•Tctex1 and dynein protein levels decreased, but α-synuclein, LC3-II and LAMP2 protein increased after Tctex1 mutation.; while α-synuclein, LC3-II and LAMP2 proteins were reduced in Tctex1 overexpression cell lines, with the same trend was found in mRNA levels.•Our results suggest that Tctex1 mutants interference lead to Tctex1 downregulation and dysfunction. Tctex-1 overexpression promoted autophagy lysosome fusion and effectively degraded α-synuclein with increased cell activity. Tctex1 is an important structure of dynein light chain in mammalian cells, clarifying the role of Tctex1 in α-synuclein autophagy lysosomal degradation may offer insights into the formation of Lewy bodies and neuronal death. We constructed dsRED-N1-Tctex1 overexpression, pDsRED2-N1-Tctex1(T94E) mutation and transfected into SH-SY5Y cells. Relative protein expression was measured by Western Blot and mRNA levels were measured by real-time quantitative PCR. Confocal microscopy was used to observe their sublocalizations in cells. We found that: WST assay results show that cell activity decreased after Tctex1 mutation (T94E), while Tctex1 overexpression increased cell activity. In Tctex1 mutation transfected cell lines Tctex1 and dynein protein levels decreased; α-synuclein, LC3-II and LAMP2 protein increased. However, α-synuclein, LC3-II and LAMP2 proteins were reduced in Tctex1 overexpression cell lines, with the same trend was found in mRNA levels. In Tctex1 mutation transfected cell lines Tctex1 fluorescence intensity weakened; α-synuclein, LC3-II and LAMP2 fluorescence was enhanced, while α-synuclein, LC3-II and LAMP2 weakened in Tctex1 overexpressing cells. Our results suggest that Tctex1 mutants interference lead to Tctex1 downregulation and dysfunction. Tctex1 overexpression promoted autophagy lysosome fusion and effectively degraded α-synuclein with increased cell activity. Thus, Tctex1 plays an important role in α-synuclein autophagic degradation.