STUB1/CHIP is required for HIF1A degradation by chaperone-mediated autophagy

Abstract

The transcription factor hiF1 is mostly regulated by the oxygen-dependent proteasomal degradation of the labile subunit hiF1A. recent data showed degradation of hiF1A in the lysosome through chaperone-mediated autophagy (cMA). however the molecular mechanism involved has not been elucidated. This study shows that the KFerQ-like motif, that has been identified in all cMA substrates, is required to mediate the interaction between hiF1A and the chaperone hSpA8. Moreover, mutations in the KFerQ-like motif of hiF1A preclude the interaction with the cMA receptor LAMp2A, thus inhibiting its lysosomal degradation. importantly, we show for the first time that the ubiquitin ligase STUB1 is required for degradation of hiF1A in the lysosome by cMA. indeed, mutations in STUB1 that inhibit either the ubiquitin ligase activity or its ability to bind to hSpA8, both prevent degradation of hiF1A by cMA. Moreover, we show that hiF1A binds to and is translocated into intact lysosomes isolated from rat livers. This new pathway for degradation of hiF1A does not depend on the presence of oxygen and is activated in response to nutrient deprivation such that the levels of hiF1A bound to cMA positive lysosomes significantly increase in starved animal livers and the binding of hiF1A to LAMp2A increases in response to serum deprivation. Moreover, excessive degradation of hiF1A by cMA compromises cells' ability to respond to and survive under hypoxia, suggesting that this pathway might be of pathophysiological importance in conditions that combine hypoxia with starvation. leucinylleucinylleucinal/proteasome inhibitor; MTT, 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide; RCC, renal cell carcinoma; Serpinb, serpin peptidase inhibitor, clade B/Ovalbumin; SLC2A1, solute carrier family 2 (facilitated glucose transporter)/glucose transporter; STUB1, STIP1 homology and U-box containing protein 1; TPR, tetratricopeptide repeat; UPS, ubiquitin-proteasome system; VEGFA, vascular endothelial growth factor A; u-box, modified RING finger domain lacking the metal-chelating residues

Cyclin-dependent kinases regulate lysosomal degradation of hypoxia-inducible factor 1α to promote cell-cycle progression

“…Mechanisms by which HIF-1α is regulated in an O 2 -independent manner have also been identified (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26). In addition to proteasome-dependent pathways for HIF-1α degradation, we identified a pathway by which HIF-1α can be targeted for lysosomal degradation through chaperonemediated autophagy (27), which subsequently was confirmed by others (28)(29)(30).…”

Chaperone-mediated autophagy: roles in disease and aging

“…Recent studies have demonstrated that CMA is activated during hypoxia and this activation is required for cell survival [38]. Although the specific substrates degraded by CMA under these conditions are not fully elucidated, the fact that the hypoxia-inducible factor 1 has been confirmed as a CMA substrate [39] supports a possible regulatory effect of CMA on the intensity and duration of the cellular response to hypoxia.…”

Autophagy degrades hypoxia inducible factors

“…5 Interestingly, the E3 ligase STIP1 homology and U-box containing protein 1 (STUB1, also known as CHIP), but not VHL, was shown to be required for CMA-mediated HIF1a degradation. 6 Furthermore, STUB1 mediated K63 ubiquitination in an oxygen-independent manner and was required for HIF1a degradation via CMA. 7 We identified a canonical KFERQ motif (LDKFQ) and a putative KFERQ motif (QVKVY, if Y gets phosphorylated) in human HIF2a, which raises the possibility that CMA also mediates HIF2a degradation in a similar manner.…”