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Canonical autophagy dependent on the class III phosphoinositide-3 kinase Vps34 is required for naive T-cell homeostasis.

ABSTRACT: The homeostasis of naive T cells is essential for protective immunity against infection, but the cell-intrinsic molecular mechanisms that control naïve T-cell homeostasis are poorly understood. Genetic ablation in lower organisms has revealed a critical role for Vps34, an evolutionary conserved class III phosphoinositide-3 kinase (PI3K), in regulating endocytosis and autophagy; however, the physiological function of Vps34 in the immune system, especially in T cells, is unclear. Here we report that Vps34 is required for the maintenance of naïve T cells, acting in a cell-intrinsic manner. T-cell-specific deletion of the gene encoding Vps34 resulted in reduced stability of Vps15 and Beclin-1, components of the class III PI3K complex, and impaired autophagy in T cells. Vps34 was dispensable for T-cell development but important for the survival of naïve T cells. Vps34-deficient T cells showed increased mitochondrial mass and accumulation of reactive oxygen species, consistent with deficient removal of damaged mitochondria. Thus, Vps34-dependent canonical autophagy plays a critical role in maintaining T-cell homeostasis by promoting T-cell survival through quality control of mitochondria.

SUBMITTER: Willinger T

PROVIDER: S-EPMC3365213 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature

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Canonical autophagy dependent on the class III phosphoinositide-3 kinase Vps34 is required for naive T-cell homeostasis.

Willinger Tim T Flavell Richard A RA

Proceedings of the National Academy of Sciences of the United States of America 20120516 22

The homeostasis of naive T cells is essential for protective immunity against infection, but the cell-intrinsic molecular mechanisms that control naïve T-cell homeostasis are poorly understood. Genetic ablation in lower organisms has revealed a critical role for Vps34, an evolutionary conserved class III phosphoinositide-3 kinase (PI3K), in regulating endocytosis and autophagy; however, the physiological function of Vps34 in the immune system, especially in T cells, is unclear. Here we report th ...[more]

PMID: 22592798

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Project description:The Vps34 (vacuolar protein sorting 34) class III PI3K (phosphoinositide 3-kinase) phosphorylates PtdIns (phosphatidylinositol) at endosomal membranes to generate PtdIns(3)P that regulates membrane trafficking processes via its ability to recruit a subset of proteins possessing PtdIns(3)P-binding PX (phox homology) and FYVE domains. In the present study, we describe a highly selective and potent inhibitor of Vps34, termed VPS34-IN1, that inhibits Vps34 with 25 nM IC50 in vitro, but does not significantly inhibit the activity of 340 protein kinases or 25 lipid kinases tested that include all isoforms of class I as well as class II PI3Ks. Administration of VPS34-IN1 to cells induces a rapid dose-dependent dispersal of a specific PtdIns(3)P-binding probe from endosome membranes, within 1 min, without affecting the ability of class I PI3K to regulate Akt. Moreover, we explored whether SGK3 (serum- and glucocorticoid-regulated kinase-3), the only protein kinase known to interact specifically with PtdIns(3)P via its N-terminal PX domain, might be controlled by Vps34. Mutations disrupting PtdIns(3)P binding ablated SGK3 kinase activity by suppressing phosphorylation of the T-loop [PDK1 (phosphoinositide-dependent kinase 1) site] and hydrophobic motif (mammalian target of rapamycin site) residues. VPS34-IN1 induced a rapid ~50-60% loss of SGK3 phosphorylation within 1 min. VPS34-IN1 did not inhibit activity of the SGK2 isoform that does not possess a PtdIns(3)P-binding PX domain. Furthermore, class I PI3K inhibitors (GDC-0941 and BKM120) that do not inhibit Vps34 suppressed SGK3 activity by ~40%. Combining VPS34-IN1 and GDC-0941 reduced SGK3 activity ~80-90%. These data suggest SGK3 phosphorylation and hence activity is controlled by two pools of PtdIns(3)P. The first is produced through phosphorylation of PtdIns by Vps34 at the endosome. The second is due to the conversion of class I PI3K product, PtdIns(3,4,5)P3 into PtdIns(3)P, via the sequential actions of the PtdIns 5-phosphatases [SHIP1/2 (Src homology 2-domain-containing inositol phosphatase 1/2)] and PtdIns 4-phosphatase [INPP4B (inositol polyphosphate 4-phosphatase type II)]. VPS34-IN1 will be a useful probe to delineate physiological roles of the Vps34. Monitoring SGK3 phosphorylation and activity could be employed as a biomarker of Vps34 activity, in an analogous manner by which Akt is used to probe cellular class I PI3K activity. Combining class I (GDC-0941) and class III (VPS34-IN1) PI3K inhibitors could be used as a strategy to better analyse the roles and regulation of the elusive class II PI3K.

Project description:Background: The production of thyroid hormones [triiodothyronine (T3), thyroxine (T4)] depends on the organization of the thyroid in follicles, which are lined by a monolayer of thyrocytes with strict apicobasal polarity. This polarization supports vectorial transport of thyroglobulin (Tg) for storage into, and recapture from, the colloid. It also allows selective addressing of channels, transporters, ion pumps, and enzymes to their appropriate basolateral [Na+/I- symporter (NIS), SLC26A7, and Na+/K+-ATPase] or apical membrane domain (anoctamin, SLC26A4, DUOX2, DUOXA2, and thyroperoxidase). How these actors of T3/T4 synthesis reach their final destination remains poorly understood. The PI 3-kinase isoform Vps34/PIK3C3 is now recognized as a main component in the general control of vesicular trafficking and of cell homeostasis through the regulation of endosomal trafficking and autophagy. We recently reported that conditional Vps34 inactivation in proximal tubular cells in the kidney prevents normal addressing of apical membrane proteins and causes abortive macroautophagy. Methods: Vps34 was inactivated using a Pax8-driven Cre recombinase system. The impact of Vps34 inactivation in thyrocytes was analyzed by histological, immunolocalization, and messenger RNA expression profiling. Thyroid hormone synthesis was assayed by 125I injection and plasma analysis. Results: Vps34 conditional knockout (Vps34cKO) mice were born at the expected Mendelian ratio and showed normal growth until postnatal day 14 (P14), then stopped growing and died at ?1 month of age. We therefore analyzed thyroid Vps34cKO at P14. We found that loss of Vps34 in thyrocytes causes (i) disorganization of thyroid parenchyma, with abnormal thyrocyte and follicular shape and reduced PAS+ colloidal spaces; (ii) severe noncompensated hypothyroidism with extremely low T4 levels (0.75?±?0.62??g/dL) and huge thyrotropin plasma levels (19,300?±?10,500?mU/L); (iii) impaired 125I organification at comparable uptake and frequent occurrence of follicles with luminal Tg but nondetectable T4-bearing Tg; (iv) intense signal in thyrocytes for the lysosomal membrane marker, LAMP-1, as well as Tg and the autophagy marker, p62, indicating defective lysosomal proteolysis; and (v) presence of macrophages in the colloidal space. Conclusions: We conclude that Vps34 is crucial for thyroid hormonogenesis, at least by controlling epithelial organization, Tg iodination as well as proteolytic T3/T4 excision in lysosomes.

Project description: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.

Dataset Information

Canonical autophagy dependent on the class III phosphoinositide-3 kinase Vps34 is required for naive T-cell homeostasis.

Publications

Canonical autophagy dependent on the class III phosphoinositide-3 kinase Vps34 is required for naive T-cell homeostasis.

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