Dysferlin Protein–Protein Interaction Pathways in the Organ of Corti and Spiral Ganglion Intersect with Alzheimer’s Protein Pathways

Dysferlin direct protein–protein interactions (PPI) previously have been elucidated with surface plasmon resonance (SPR) and predicted to underlie membrane repair in mechanotransducing myofibrils. In mechanotransducing inner ear hair cells, dysferlin is detected with Z-stack confocal immunofluorescence in the stereocilia and their inserts in the tectorial membrane (TM) co-localizing with FKBP8, consistent with the SPR determination of tight, positively Ca²⁺-dependent interaction. FKBP8, a direct binding partner of mechanotransducing TMC1, when overexpressed, evokes an elevation in anti-apoptotic BCL2, inhibition of ryanodine receptor (RYR) activity, and a consequent reduction in Ca²⁺ release. RYR3 has now been immunolocalized to the tip of the TM in close association with a third-row outer hair cell (OHC) stereociliary BCL2-positive insertion. Dysferlin, annexin A2, and Alzheimer’s proteins BACE1 and amyloid precursor protein (APP) are also accumulated in these stereociliary insertions. RYR2 and RYR1 have been immunolocalized to the TM core, in position to influence TM Ca²⁺. Dysferlin PPI pathways also intersect with AD protein pathways in the spiral ganglion (SG). Dysferlin segregates with FKBP8, BACE1, and RYR3 in the interiors of SG type I cell bodies. RYR1, RYR2, PSEN1, BCL2, and caspase 3 are primarily confined to plasma membrane sites. RYR3 pathways traverse the plasma membrane to the cell body interior. Western analysis of dysferlinopathy proteins links FKBP8 and BCL2 overexpression with RYR inhibition, indicative of dysferlin targets that are ameliorative in AD.