The origins of rimmed vacuoles and granulovacuolar degeneration bodies are associated with the Wnt signaling pathway

Inclusion-body myositis (IBM) and Alzheimer's disease (AD) are biochemically characterized by the presence of aggregated β-amyloid protein and tau protein. In addition, both diseases are pathologically characterized by vacuolar changes, including rimmed vacuoles (RVs) in IBM and granulovacuolar degeneration (GVD) in AD. Previously, we demonstrated that RVs and GVD bodies are associated with a set of common molecules, leading us to speculate that both RVs and GVD bodies originate from similar structures on the plasma membrane of muscle cells and neuronal cells, namely, the neuromuscular junction (NMJ) and the postsynaptic spine especially in terms of Wnt signaling pathway. In this study, we investigated the presence of components of NMJ in RVs and/or postsynaptic spine in GVD bodies respectively by immunohistochemistry and immunofluorescence. The antigens probed included the following: (1) dishevelled (Dvl) family proteins (Dvl1, Dvl2 and Dvl3), (2) NMJ-associated proteins (low density lipoprotein-related protein 4 [Lrp4], heat shock protein 70 [Hsp70], β-catenin, phospho-β-catenin, rapsyn, P21-activated kinase 1 [PAK1], adenomatous polyposis coli [APC] and ADP-ribosylation factor 6 [Arf6]), (3) a lipid raft-associated molecule (phosphatidylinositol 4, 5-bisphosphate [PIP2]), and (4) other proteins [prion, glycogen-synthase kinase 3β (GSK-3β)]. In all cases of sporadic IBM examined, RVs were immunopositive for Dvl3, Hsp70, β-catenin, PIP2, APC, prion and GSK-3β. In all cases of AD examined, GVD bodies were immunopositive for Dvl3, phospho-β-catenin, rapsyn, APC and PIP2. These findings show that RVs and GVD bodies share common molecules associated with the Wnt signaling pathway, indicating that these structures share a common structural and functional origin.