The glycolytic enzyme PGAM1 functions as a metabolic-autophagy checkpoint to coordinate growth and stress tolerance.

Cell survival requires tight coordination between growth-promoting metabolism and cellular quality-control pathways, yet how these processes are integrated remains unclear. Here we identify the conserved glycolytic enzyme PGAM1 as a metabolic-autophagy checkpoint that links glycolysis to autophagy initiation independently of its catalytic activity. Using complementary yeast and mammalian systems we show that PGAM1 functions as a molecular scaffold that recruits phosphatidylinositol 3-kinase complex I to the phagophore assembly site, thereby licensing autophagosome biogenesis. This autophagy-regulatory function is genetically essential, evolutionarily conserved and functionally separable from glycolysis. It is regulated by Atg1/ULK1-mediated phosphorylation that enhances Atg14 binding under starvation. Functionally, PGAM1 coordinates anabolic growth and stress-induced survival to maintain cellular homeostasis. In cancer, PGAM1 upregulation enhances both glycolytic flux and autophagy capacity. Disruption of either function markedly impairs tumour growth, establishing PGAM1 as a homeostatic checkpoint that is hijacked in cancer to drive both proliferation and stress tolerance.