In this minireview, we cover the discovery of the human erythrocyte spectrin E2/E3 ubiquitin conjugating/ligating enzymatic activity and the specific cysteines involved. We then discuss the consequences when this activity is partially inhibited in sickle cell disease and the possibility that the same attenuation is occurring in multiple organ dysfunction syndrome. We finish by discussing the reasons for believing that nonerythroid spectrin isoforms (I and II) also have this activity and the importance of testing this hypothesis. If correct, this would suggest that the nonerythroid spectrin isoforms play a major role in protein ubiquitination in all cell types. This would open new fields in experimental biology focused on uncovering the impact that this enzymatic activity has upon protein-protein interactions, protein turnover, cellular signaling, and many other functions impacted by spectrin, including DNA repair.

Alzheimer's disease (AD) is a devastating neurodegenerative disease with pathological misfolding of amyloid-β protein (Aβ). The recent interest in Aβ misfolding intermediates necessitates development of novel detection methods and ability to trap these intermediates. We speculated that two regions of Aβ may allow for detection of specific Aβ species: the N-terminal and 22-35, both likely important in oligomer interaction and formation. We determined via epitomics, proteomic assays, and electron microscopy that the Aβ(42) species (wild type, ΔE22, and MetOx) predominantly formed fibrils, oligomers, or dimers, respectively. The 2H4 antibody to the N-terminal of Aβ, in the presence of 2% SDS, primarily detected fibrils, and an antibody to the 22-35 region detected low molecular weight Aβ species. Simulated molecular modeling provided insight into these SDS-induced structural changes. We next determined if these methods could be used to screen anti-Aβ drugs as well as identify compounds that trap Aβ in various conformations. Immunoblot assays determined that taurine, homotaurine (Tramiprosate), myoinositol, methylene blue, and curcumin did not prevent Aβ aggregation. However, calmidazolium chloride trapped Aβ at oligomers, and berberine reduced oligomer formation. Finally, pretreatment of AD brain tissues with SDS enhanced 2H4 antibody immunostaining of fibrillar Aβ. Thus we identified and characterized Aβs that adopt specific predominant conformations (modified Aβ or via interactions with compounds), developed a novel assay for aggregated Aβ, and applied it to drug screening and immunohistochemistry. In summary, our novel approach facilitates drug screening, increases the probability of success of antibody therapeutics, and improves antibody-based detection and identification of different conformations of Aβ.