When nutrient deficiency occurs, the cell recycles proteins and organelles to secure starting material for the production of important proteins or structures. The protein NUFIP1, which is normally located in the cell nucleus, helps in this process. The scientists observed that the protein migrates from the cell nucleus into the cytoplasm if there is A nutrient deficiency in order to attach itself to ribosomes. In this way, the ribosomes are marked for its degradation. A lack of nutrients leads to a lack of certain amino acids. This stimulates the autophagy (degradation process) in the cell.

For their investigations, the scientists exposed HEK293 cells (commercially available human embyonic kidney cells) to  a nutrient deficiency solution or exposed them to an mTORC1 signalling pathway inhibitor (TORIN1). Subsequently, they analyzed all proteins in lysosomes biochemically and by mass spectrometry. Lysosomes are responsible for degradation and recycling of macromolecules in the cell. They identified the nuclear fragile X mental retardation-interacting protein 1 (NUFIP1). Both TORIN1 and a nutrient deficiency lead to inhibition of the mTORC1 signalling pathway, which controls cell growth, division and survival. The researcher were particularly interested in the protein NUFIP1. Without NUFIP1, the cells are not able to eleminate superfluous balast at a lack of nutrients.

The scientists presented their work in Journal Science:
Gregory A. Wyant, Monther Abu-Remaileh, Evgeni M. Frenkel, Nouf N. Laqtom, Vimisha Dharamdasani, Caroline A. Lewis, Sze Ham Chan, Ivonne Heinze, Alessandro Ori, David M. Sabatini (2018). NUFIP1 is a ribosome receptor for starvation-induced ribophagy. Science eaar2663, DOI: 10.1126/science.aar2663.

Source:
https://www.leibniz-gemeinschaft.de/medien/aktuelles/news-details/article/ueberleben_bei_hunger_100003471/