Governance Threshold Failure Across Substrates: P50 Sensory Gating and p53 Tumor Suppression as IE-THRESHOLD Operations (HLRP Paper #128)

This paper identifies P50 sensory gating (neural) and p53 tumor suppression (cellular) as parallel IE-THRESHOLD operations within Geometric Coupling Theory. Both systems operate as governance checkpoints: P50 gates sensory signal at the neural level (S2/S1 ratio <0.50 = normal), while p53 gates cellular replication at the genomic level. The inverse epidemiological relationship between schizophrenia and cancer — documented reduced cancer incidence in schizophrenia patients — is reframed as governance load shifting between substrates under a fixed single-copy governance budget. Includes comparison table (8 properties), 2×2 population matrix, 5 falsification criteria, and GCT corpus cross-reference. Part of the GCT/HLRP corpus.