Project Grant R21NS135426

DETERMINING PATHOGENIC PRPC-INDUCED SIGNALING PATHWAYS IN HUMAN IPSC-INDUCED NEURONS - PRION DISEASES ARE RARE, INVARIABLY FATAL NEURODEGENERATIVE DISORDERS CHARACTERIZED BY RAPID COGNITIVE AND MOTOR DECLINE. CERTAIN PATHOLOGIC FEATURES OVERLAP WITH ALZHEIMER'S DISEASE, INCLUDING PROTEIN AGGREGATES AND MASSIVE SYNAPSE LOSS IN THE BRAIN, YET THE SEQUENCE OF EVENTS DRIVING SYNAPTIC LOSS IS INCOMPLETELY UNDERSTOOD. IN PRION AND ALZHEIMER'S DISEASE MODELS, NEURONAL CELLULAR PRION PROTEIN (PRPC) REPORTEDLY BINDS OLIGOMERS AND ELICITS A CASCADE OF INTRACELLULAR SIGNALS, WHEREAS PRPC DELETION AMELIORATES SYNAPTIC IMPAIRMENT, STRONGLY IMPLICATING NEURONAL PRPC IN ALTERING SIGNAL TRANSDUCTION EVENTS. USING UNBIASED TRANSCRIPTOMICS ON PRION- INFECTED MOUSE BRAIN, WE HAVE FOUND THAT IMMEDIATE EARLY GENES ARE AMONG THE EARLIEST, MOST SIGNIFICANTLY UPREGULATED GENES IN THE HIPPOCAMPUS, SUGGESTIVE OF HEIGHTENED NEURONAL ACTIVITY. WE HAVE ALSO DISCOVERED EARLY ABERRANT NEURONAL KINASE ACTIVITY IN THE HIPPOCAMPUS AND CORTEX. NOTABLY, SIMILAR KINASE MODIFICATIONS WERE INCITED IN HUMAN IPSC-INDUCED NEURONS WITHIN 2 HOURS OF TRIGGERING PRPC. IN AIM 1, WE WILL DETERMINE HOW AN ANTI-PRP ANTIBODY LIGAND OR PURIFIED INFECTIOUS PRION OLIGOMERS INDUCE SYNAPTIC KINASE SIGNALING IN HUMAN IPSC-INDUCED NEURONS. IN AIM 2, WE USE HIGHLY SENSITIVE AND QUANTITATIVE PROTEOMICS TO IDENTIFY THE PRPC- TRANSMEMBRANE SIGNALING NETWORK COMPONENTS AND NETWORK ALTERATIONS IN HUMAN NEURONS TRIGGERED BY A PRION PROTEIN LIGAND. THESE STUDIES ARE THE FIRST TO PURSUE PRPC-INITIATED SIGNALING PATHWAYS IN HUMAN NEURONS, AND ARE EXPECTED TO ESTABLISH THE SIGNALING PARAMETERS AND DOWNSTREAM CONSEQUENCES AS WELL AS PROVIDE INSIGHT INTO EVENTS LEADING TO SYNAPSE LOSS IN DISEASE.