Mtmr shcool web series#
It consists of a series of endosomes: early endosomes (EEs), recycling endosomes (REs), late endosomes (LEs), and lysosomes (LYs). The endocytic pathway has multiple functions including degradation and recycling of macromolecules and signaling to the cytosol and nucleus, thus playing an essential role in cell homeostasis.
These findings indicate that MTMR4 is essential for the integrity of endocytic and autophagic pathways. Notably, MTMR4 knockdown inhibited the nuclear translocation of starvation stress responsive transcription factor-EB (TFEB) with reduced expression of lysosome-related genes in starved cells. In amino acid- and serum-starved cells, MTMR4 knockdown decreased both autophagosomes and autolysosomes and markedly increased PI(3)P-containing autophagosomes and late endosomes, suggesting that the fusion with lysosomes of autophagosomes and late endosomes might be impaired. MTMR4 knockdown markedly suppressed the motility, fusion, and fission of PI(3)P-enriched structures, resulting in decreases in late endosomes, autophagosomes, and lysosomes, and enlargement of PI(3)P-enriched early and late endosomes.
MTMR4 was localized mainly in late endosomes and autophagosomes. We investigated the subcellular distribution and functions of myotubularin-related protein-4 (MTMR4), which is distinct among other MTMRs in that it possesses a PI(3)P-binding FYVE domain, in lung alveolar epithelium-derived A549 cells. Phosphoinositide levels are tightly regulated by lipid-kinases and -phosphatases however, a phosphatase that converts PI(3)P back to phosphatidylinositol in the endosomal and autophagosomal compartments is not fully understood. Phosphatidylinositol 3-phosphate (PI(3)P) is the predominant phosphoinositide species in early endosomes and autophagosomes, in which PI(3)P dictates traffic of these organelles.
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