Graduate School of Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8021, Japan.
Graduate School of Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8021, Japan; Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8021, Japan; Research Institute of Green Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8021, Japan.
Biochem Biophys Res Commun. 2024 Nov 19;734:150628. doi: 10.1016/j.bbrc.2024.150628. Epub 2024 Aug 31.
Microautophagy degrades cargos in the vacuole by direct engulfment of the vacuolar membrane. Micronucleophagy selectively degrades a portion of the nucleus in budding yeast. The vacuole contacts the nucleus via the nucleus-vacuole junction (NVJ), and in micronucleophagy a portion of the nucleus containing nucleolar proteins is made to protrude into the vacuole at the NVJ, followed by abscission and degradation. Microautophagy and micronucleophagy are induced by inactivation of target of rapamycin complex 1 (TORC1) protein kinase after nutrient starvation. Here, we show that the VAMP-associated proteins (VAPs) Scs2 and its paralog Scs22 are required for NVJ integrity and micronucleophagic degradation of nucleolar proteins. On the other hand, nucleolar dynamics prerequisite for micronucleophagy were not impaired in VAP mutant cells. Finally, yeast VAPs were critical for viability during prolonged nutrient starvation. This study sheds light on the emerging role of VAP in adaptation in responses to nutrient starvation.
微自噬通过直接吞噬液泡膜来降解液泡中的货物。微核噬作用选择性地降解出芽酵母细胞核的一部分。液泡通过核-液泡连接（NVJ）与细胞核接触，在微核噬作用中，含有核仁蛋白的一部分细胞核被推向 NVJ 处的液泡，然后分离和降解。微自噬和微核噬作用是在营养饥饿后靶蛋白雷帕霉素复合物 1（TORC1）蛋白激酶失活时诱导的。在这里，我们表明 VAMP 相关蛋白（VAPs）Scs2 及其旁系同源物 Scs22 是 NVJ 完整性所必需的，也是核仁蛋白微核噬作用降解所必需的。另一方面，VAP 突变细胞中核仁动力学对于微核噬作用是必需的。最后，酵母 VAP 在长时间营养饥饿时对生存至关重要。这项研究揭示了 VAP 在适应营养饥饿反应中的新作用。
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