Background: PTEN is targeted by multiple E3 ligases but that does not clearly decipher the rigid control of its level and activity. Results: CHIP interacts with PTEN and promotes its proteasomal degradation. Conclusion: CHIP acts as a bridge between the chaperone system and the degradation machinery for PTEN. Significance: Stabilization of PTEN by targeting CHIP can be a novel therapeutic approach in cancer regulation.

Highlights d SARS-CoV-2 infection in induced lung cells is characterized by phosphoproteomics d Analysis of response reveals host cell signaling and protein expression profile d Comparison to studies in undifferentiated cell lines shows unique pathology in iAT2s d Systems-level predictions find druggable pathways that can impede viral life cycle

c-Myc is a proto-oncogenic transcription factor and its rapid turnover mediated by the ubiquitin-proteasome system is critical for maintaining normal cellular homeostasis. Multiple ubiquitin ligases have been assigned for c-Myc regulation till date. However, the available data suggest for the possible existence of additional E3 ligase(s). Here, we report a new E3 ligase for c-Myc, the carboxyl terminus of Hsc70-interacting protein or CHIP, which is a chaperone-associated Ubox-containing E3 ligase. In this report, we show that CHIP interacts and ubiquitinates c-Myc, thus targeting it for proteasome-mediated degradation. Overexpression of CHIP could accelerate the turnover rate of c-Myc protein. Conversely, knockdown of CHIP by RNAi stabilizes endogenous c-Myc. The interaction between CHIP and c-Myc depends on the N-terminally located tetratricopeptide repeats of CHIP, which has been implicated as a chaperone-binding motif. Inhibition of Hsp90 chaperone activity by 17-N-allylamino-17-demethoxygeldanamycin reduces c-Myc protein level. We found that the association between CHIP and c-Myc is dependent on the chaperones; particularly Hsp70. CHIP antagonizes the transcriptional activity of c-Myc and decreases the abundance of the transcripts of its target genes. Overall, CHIP-knockdown increases malignant behavior of C6 glioma cells. To the best of our knowledge, this is the first report of c-Myc being regulated by a bona-fide chaperone-associated E3 ligase in HEK293 as well as glioma cells. Because CHIP has been reported earlier to be negatively regulating Akt1, BCR-ABL and hTERT, and now c-Myc, the present study may strengthen the view that CHIP acts as a tumor suppressor.