ANTIPRIONS: A SCREEN FOR PRION MUTANTS INTERFERING WITH ENDOGENOUS PRION AGGREGATION

PRIONS AND AMYLOID PRION-LIKE AGGREGATES HAVE BEEN DIRECTLY IMPLICATED IN MORE THAN 20 HUMAN DISEASES, AMONG THEM NEURODEGENERATIVE PATHOLOGIES SUCH AS ALZHEIMER¿S, PARKINSON¿S, AND HUNTINGTON¿S DISEASES. PRION PROTEINS ARE SELF-PROPAGATING AND TRANSMISSIBLE PROTEIN ISOFORMS THAT ACCUMULATE AS LARGE STRUCTURE-DRIVEN AGGREGATES, AND IT IS GENERALLY ACCEPTED THAT PRION ACCUMULATION IN THE HUMAN BRAIN IS A DIRECT CAUSE OF NEURONAL DEGENERATION. HOWEVER, APPROPRIATE THERAPEUTIC APPROACHES AND EFFECTIVE TREATMENTS ARE LARGELY LACKING, AND EFFORTS TO PREVENT OR DECREASE THE RATE OF PRION AGGREGATION WITH PEPTIDES HAVE PRODUCED VERY LIMITED RESULTS. HERE WE HYPOTHESIZE THAT, SIMILARLY TO THE OPPOSING TWINS PROMETHEUS AND EPIMETHEUS, ANTIPRIONS COULD ORIGINATE FROM PRION DOMAINS AS QUASI-TWIN STRUCTURES THAT (1) STILL BIND WITH HIGH EFFICIENCY TO PRION AGGREGATES BUT (2) DO NOT TRANSMIT THE PATHOLOGICAL FOLD TO NEWLY RECRUITED MONOMERS, THUS ARRESTING PRION AGGREGATE GROWTH. GIVING SUPPORT TO THIS HYPOTHESIS, PRION MISFOLDING AND AGGREGATION TAKES PLACE IN SUCCESSIVE STEPS OF CONFORMATIONAL CHANGE. HOWEVER, THE STRUCTURAL DETAILS OF THESE TRANSITIONS ARE LARGELY UNKNOWN, MAKING IMPOSSIBLE THE POST HOC DESIGN OF MUTANTS BASED ON PREDICTED STRUCTURAL PROPERTIES. FOR THIS REASON, OUR PROPOSAL IS GROUNDED IN A NON-BIASED APPROACH, AND PLANS TO USE HUMAN PRION SEQUENCES (Aand 946;42 AND and 945;SYN) AS INITIALS SEEDS TO PERFORM (1) AN UNPRECEDENTED, EXTENSIVE AND HIGHLY SENSITIVE RANDOM-MUTAGENESIS BASED SCREEN DESIGNED TO GENERATE AND TEST MORE THAN TEN MILLION INDEPENDENT MUTANT PEPTIDES AS ANTIPRION FACTORS, AND (2) A COMPREHENSIVE FUNCTIONAL SURVEY OF THE ISOLATED ANTIPRION PEPTIDES BY THEIR ABILITY TO COUNTERACT AGGREGATION OF HUMAN PRIONS AND THEIR CONCOMITANT PATHOLOGICAL EFFECTS IN NEURONS.