INTRACELLULAR AGGREGATION OF A PDK1 SUBSTRATE BY BLOCKING THE CONFORMATIONAL SENSOR POCKET ON PDK1

BIONDI, RICARDO M.; LEROUX, ALEJANDRO E.

Salta

Congreso; LV Reunión Científica anual SAIB y XIV congreso de PABMB; 2019

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

Conformationaldisorders are a group of pathologies that share aggregation of specificproteins as a common feature. They include the prion disease, Alzheimer?sdisease, diverse tauopathies, and Parkinson?s disease. There is no successfuldisease-modifying treatment yet available for any of the conformationaldisorders, possibly because we lack detailed molecular understanding of themechanisms that cause them. The seeding hypothesis is considered to be thegeneral mechanism explaining the aggregation. Nevertheless, even after 20 yearsof being accepted, aggregation by seeding remains vastly inefficient incell-free assays and cannot explain the existence of ?strains? of proteins thataggregate.Thephosphoinositide-dependent protein kinase 1 (PDK1) is a master kinase thatphosphorylates the activation loop site and is required for the activity of atleast 23 other AGC kinases. Some of the substrates, like PKCs, areconstitutively phosphorylated while others, like S6K and Akt/PKB, aredynamically phosphorylated by PDK1. Protein kinase C zeta (PKCzeta), and itsbrain specific splice variant PKMzeta, have important roles in late long-termpotentiation and long-term memory. Additionally, PKCzeta/ PKMzeta aggregatesare present in the neurofibrillary tangles that affect brain function ofAlzheimer?s disease patients.We have previouslydescribed the mechanisms used by PDK1 to sense the conformation of itssubstrates during cell signaling. We now show through a variety of techniques thatblocking the ?conformational sensor? pocket on PDK1 can trigger the cellular aggregationof PKCzeta. Based on our results, we elaborated a novel hypothesis that canexplain how proteins aggregate in conformational disorders and the existence of?strains?. The main goal of the follow-up project is to identify specificconformational sensors that are responsible for the cellular aggregation ofTau, alpha-synuclein, and p62/SQSTM1, all proteins that aggregate inconformational disorders. We envisage that the identification of the ?conformationalsensors? and the actual mechanisms involved in protein aggregation will enabledevelopment of innovative drugs that target the original cause of major globaldiseases that have high unmet medical need.