Prolonged glutamine starvation reactivates mTOR to inhibit autophagy and initiate autophagic lysosome reformation to maintain cell viability

• Published in: The international journal of biochemistry & cell biology 2024-12, Vol.177, p.106694, Article 106694
• Main Authors: Singh, Amruta, Mahapatra, Kewal Kumar, Praharaj, Prakash Priyadarshi, Patra, Srimanta, Mishra, Soumya Ranjan, Patil, Sankargouda, Bhutia, Sujit Kumar
• Format: Article
• Language: English
• Subjects: Autolysosome; Autophagic lysosome reformation; Autophagy; Autophagy - drug effects; Cell Line, Tumor; Cell Survival - drug effects; Clathrin - metabolism; Glutamine - deficiency; Glutamine - metabolism; Humans; Lysosomes - drug effects; Lysosomes - metabolism; Mammalian target of rapamycin; Proto-lysosome; rab GTP-Binding Proteins - genetics; rab GTP-Binding Proteins - metabolism; rab7 GTP-Binding Proteins; TOR Serine-Threonine Kinases - metabolism
• ISSN: 1357-2725; 1878-5875; 1878-5875
• DOI: 10.1016/j.biocel.2024.106694

Autophagy, a cellular recycling mechanism, utilizes lysosomes for cellular degradation. Prolonged autophagy reduces the pool of functional lysosomes in the cell. However, lysosomal homeostasis is maintained through the regeneration of functional lysosomes during the terminal stage of autophagy, i.e. Autophagic lysosome reformation (ALR). Through confocal microscopy during glutamine starvation, we unravel the regeneration of tubules from autolysosomes by undertaking significant membrane remodeling, which majorly depends on mTOR reactivation, RAB7 dissociation, phosphatidyl inositol 3 phosphate (PI3P) dependent-dynamin 2 and clathrin recruitment. In glutamine-starved cells, we found mTOR is the central modulator in regulating ALR initiation, and its pharmacological inhibition with rapamycin leads to a decrease in lysosomal tubulation. Moreover, RAB7 and Clathrin are essential for tubule elongation and it showed that siRNA targeting RAB7 and Clathrin restricts tubule initiation under glutamine starvation. In this setting, we examined the physiological relevance of ALR during prolonged glutamine deprivation and found that genetic and pharmacological inhibition of critical proteins involved in ALR promotes cell death in oral cancer cells, establishing ALR is essential for maintaining cell survival during stress. [Display omitted] •Glutamine starvation-induced autophagy regulates ALR in oral cancer cells.•mTOR reactivation under prolonged glutamine starvation induces ALR in oral cancer cells.•RAB7 and Clathrin are essential to induce ALR in oral cancer cells.•ALR induction under prolonged glutamine starvation is cytoprotective.