UVRAG cooperates with cargo receptors to assemble the ER-phagy site.

ER-phagy is a selective autophagy process that targets specific regions of the endoplasmic reticulum (ER) for removal via lysosomal degradation. During cellular stress induced by starvation, cargo receptors concentrate at distinct ER-phagy sites (ERPHS) to recruit core autophagy proteins and initiate ER-phagy. However, the molecular mechanism responsible for ERPHS formation remains unclear. In our study, we discovered that the autophagy regulator UV radiation Resistance-Associated Gene (UVRAG) plays a crucial role in orchestrating the assembly of ERPHS. Upon starvation, UVRAG localizes to ERPHS and interacts with specific ER-phagy cargo receptors, such as FAM134B, ATL3, and RTN3L. UVRAG regulates the oligomerization of cargo receptors and facilitates the recruitment of Atg8 family proteins. Consequently, UVRAG promotes efficient ERPHS assembly and turnover of both ER sheets and tubules. Importantly, UVRAG-mediated ER-phagy contributes to the clearance of pathogenic proinsulin aggregates. Remarkably, the involvement of UVRAG in ER-phagy initiation is independent of its canonical function as a subunit of class III phosphatidylinositol 3-kinase complex II.

UVRAG: orchestrating the initiation of reticulophagy.

Reticulophagy is a selective autophagy of the endoplasmic reticulum (ER) mediated by cargo receptors. It plays a crucial role in ER quality control, yet the mechanisms that initiate reticulophagy remain poorly understood. Our study identified the multifunctional protein UVRAG (UV radiation resistance associated gene) as a novel regulator of reticulophagy. UVRAG interacts with sheet and tubular reticulophagy receptors, regulates the oligomerization of receptors and facilitates their interaction with LC3/GABARAP, critical for ER fragmentation and autophagosome targeting. Remarkably, we found that UVRAG's function in reticulophagy initiation is independent of its traditional role in macroautophagy. Furthermore, UVRAG enhances the degradation of ER-associated mutant proteins linked to diseases like diabetes. Our findings offer insights into the mechanisms of reticulophagy initiation and highlight UVRAG's therapeutic potential in ER-related diseases.

Phosphorylated STYK1 restrains the inhibitory role of EGFR in autophagy initiation and EGFR-TKIs sensitivity.

Epidermal growth factor receptor (EGFR) plays critical roles in cell proliferation and tumorigenesis. Autophagy has emerged as a potential mechanism involved in the acquired resistance to anti-EGFR treatments, however, the molecular mechanisms has not been fully addressed. In this study, we identified EGFR interacts with STYK1, a positive autophagy regulator, in EGFR kinase activity dependent manner. We found that EGFR phosphorylates STYK1 at Y356 site and STYK1 inhibits activated EGFR mediated Beclin1 tyrosine phosphorylation and interaction between Bcl2 and Beclin1, thus enhances PtdIns3K-C1 complex assembly and autophagy initiation. We also demonstrated that STYK1 depletion increased the sensitivity of NSCLC cells to EGFR-TKIs in vitro and in vivo. Moreover, EGFR-TKIs induced activation of AMPK phosphorylates STYK1 at S304 site. STYK1 S304 collaborated with Y356 phosphorylation to enhance the EGFR-STYK1 interaction and reverse the inhibitory effects of EGFR to autophagy flux. Collectively, these data revealed new roles and cross-talk between STYK1 and EGFR in autophagy regulation and EGFR-TKIs sensitivity in NSCLC.

Advances in ER-Phagy and Its Diseases Relevance.

As an important form of selective autophagy in cells, ER-phagy (endoplasmic reticulum-selective autophagy), the autophagic degradation of endoplasmic reticulum (ER), degrades ER membranes and proteins to maintain cellular homeostasis. The relationship between ER-phagy and human diseases, including neurodegenerative disorders, cancer, and other metabolic diseases has been unveiled by extensive research in recent years. Starting with the catabolic process of ER-phagy and key mediators in this pathway, this paper reviews the advances in the mechanism of ER-phagy and its diseases relevance. We hope to provide some enlightenment for further study on ER-phagy and the development of novel therapeutic strategies for related diseases.

STYK1 promotes autophagy through enhancing the assembly of autophagy-specific class III phosphatidylinositol 3-kinase complex I.

Macroautophagy/autophagy plays key roles in development, oncogenesis, and cardiovascular and metabolic diseases. Autophagy-specific class III phosphatidylinositol 3-kinase complex I (PtdIns3K-C1) is essential for autophagosome formation. However, the regulation of this complex formation requires further investigation. Here, we discovered that STYK1 (serine/threonine/tyrosine kinase 1), a member of the receptor tyrosine kinases (RTKs) family, is a new upstream regulator of autophagy. We discovered that STYK1 facilitated autophagosome formation in human cells and zebrafish, which was characterized by elevated LC3-II and lowered SQSTM1/p62 levels and increased puncta formation by several marker proteins, such as ATG14, WIPI1, and ZFYVE1. Moreover, we observed that STYK1 directly binds to the PtdIns3K-C1 complex as a homodimer. The binding with this complex was promoted by Tyr191 phosphorylation, by means of which the kinase activity of STYK1 was elevated. We also demonstrated that STYK1 elevated the serine phosphorylation of BECN1, thereby decreasing the interaction between BECN1 and BCL2. Furthermore, we found that STYK1 preferentially facilitated the assembly of the PtdIns3K-C1 complex and was required for PtdIns3K-C1 complex kinase activity. Taken together, our findings provide new insights into autophagy induction and reveal evidence of novel crosstalk between the components of RTK signaling and autophagy. Abbreviations: AICAR: 5-aminoimidazole-4-carboxamide ribonucleotide; AMPK: adenosine 5'-monophosphate (AMP)-activated protein kinase; ATG: autophagy related; ATP: adenosine triphosphate; BCL2: BCL2 apoptosis regulator; BECN1: beclin 1; Bre A: brefeldin A; Co-IP: co-immunoprecipitation; CRISPR: clustered regularly interspaced short palindromic repeats; DAPI: 4',6-diamidino-2-phenylindole; EBSS: Earle's balanced salt solution; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; GSEA: gene set enrichment analysis; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; MAPK8/JNK1: mitogen-activated protein kinase 8; mRFP: monomeric red fluorescent protein; MTOR: mechanistic target of rapamycin kinase; MTT: 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4: phosphoinositide-3-kinase regulatory subunit 4; qRT-PCR: quantitative reverse transcription PCR; RACK1: receptor for activated C kinase 1; RUBCN: rubicon autophagy regulator; siRNA: small interfering RNA; SQSTM1: sequestosome 1; STYK1/NOK: serine/threonine/tyrosine kinase 1; TCGA: The Cancer Genome Atlas; Ub: ubiquitin; ULK1: unc-51 like autophagy activating kinase 1; UVRAG: UV radiation resistance associated; WIPI1: WD repeat domain, phosphoinositide interacting 1; ZFYVE1: zinc finger FYVE-type containing 1.