A context dependent role of autophagy has been implicated in cancer, and modulation of autophagy has becoming a new experimental strategy in cancer treatment. Sequestosome1 (SQSTM1/p62) is a known autophagy adaptor and mediates cell proliferation, survival and death through multiple signaling pathways, includingmTORC1activationandautophagy.Accumulationandmisregulationofp62hasbeenlinkedtotumor formation, progression and resistance to therapy, thus p62 is emerging as a new therapeutic target in cancer treatment. Recent studies from our lab and others revealed a critical role of p62 in the autophagic cascade responsible for sequestration of misfolded proteins generated during endoplasmic reticulum (ER) stress, and importantly,smallmoleculestargetingtheZZdomainofp62(p62ZZ)havebeenshowntoinhibitmultiplemyeloma (MM)cellgrowth.Yethowp62ZZligandsinhibitsMMcellgrowthandmorebroadly,howp62sensesstressand regulatescellularpathwaysarestillnotfullyunderstood.Wealsofoundthatp62ZZbindshistoneH3tail,linking thechromatintargetingofp62toarecentlydiscoveredroleofp62inDNAdamageresponse,whichisfrequently targetedincancertherapeutics.MMisstillanuncurbablebloodcancertodayandischaracterizedbyconstitutive high ER-stress. We hypothesize that the conformational state and intracellular level of p62, controlled by its interaction with cellular signals, is the determinant to activate a specific pathway suchas mTORC1activation, autophagyandDNArepair.Treatingcellswithp62ligandshijacksp62andinhibitsitsnormalfunction,leading to accumulation of stress and cell growth suppression. This application aims to determine the mechanism of action that directly targeting p62ZZ inhibits MM cell growth (Aim1);? elucidate the molecular mechanisms underlyingp62-dependent selectiveactivationofmTORC1orautophagypathways(Aim2);?anddefinetherole of p62 chromatin targeting in DNA damage response (Aim3). The K99 phase of the proposed studies will be conducted under the mentorship of Dr. Tatiana Kutateladze, who is a well-regarded structural biologist in the epigenetics fieldand hasa strong record in mentoring young scientists. For the cellularexperiments relatedto autophagyand DNA damage response, I will learn from and collaborate with Dr. Andrew Thorburn, a leading expert in the field of autophagy, and Dr. Joshua Black who is an expert in chromatin biology. My progress in researchandcareerdevelopmentwillbecloselymonitoredbythededicativeandsupportiveadvisorycommittee. The goal for the K99 phase is to complete Aim1 and initiate the rest aims of the proposal and build a strong foundation for my transition to becoming an independent investigator. My long-term goal is to elucidate the mechanisms of p62-dependent signaling and regulatory pathways, using multidisciplinary approaches, particularlythosehavebeenimplicatedinhumandiseases.AK99grantwouldgreatlyaidmebyprovidingcritical training,helpingmesecureafacultypositionandallowingmetostartmycareerasanindependentresearcher.
CancercellsrelyonmTORC1pathwayandautophagytocoordinatenutrientandstresssignalsforsurvivaland progression, and modulating autophagy has becoming an emerging experimental strategy to fight cancer development and resistance to treatment. However, the exact mechanismsof autophagy machinery and its regulationarestillnotfullyunderstood.Theproposedresearchisaimedatelucidatingthebasicbiologyofp62, anautophagyadaptorandsignalinghub,byusingamultidisciplinaryapproach.