Protoporphyrin-IX nanostructures modulate their protein aggregation ability via differential oxidation and protein binding

Abstract

Porphyrias are caused by genetic defects in the heme biosynthetic pathway and are associated with accumulation of high levels of porphyrins that become cytotoxic. Porphyrins, due to their amphipathic nature, spontaneously associate into different nanostructures but very little is known about the effect of porphyrin speciation on the cytotoxic effects of porphyrins. Previously we demonstrated the unique ability of fluorescent biological porphyrins, including protoporphyrin IX (PP-IX), to cause organelle selective protein aggregation, which we posit to be a major mechanism by which porphyrins exerts their cytotoxic effect. Herein, we tested the hypothesis that PP-IX-mediated protein aggregation is modulated by different PP-IX nanostructures via a mechanism that depends on their oxidizing potential and protein binding ability. We demonstrate that PP-IX nanostructure formation is reversible in nature, and that nanostructure size modulates consequent protein oxidation and aggregation potential. We also show that albumin, the most abundant serum protein, preferentially binds PP-IX dimers and enhances their oxidizing ability. Additionally, extracellular albumin protects from intracellular porphyrinogenic stress and protein aggregation by acting as a PP-IX sponge. This work highlights the importance of PP-IX speciation in the context of the porphyrias, and offers insights into potential novel therapeutic approaches.

Irradiation of ZnPPIX Complexed with Bovine β-Lactoglobulin Causes Chemical Modifications and Conformational Changes of the Protein

“…This is likely caused by the fact that, despite our sample preparation, smaller oligomers of the ZnPPIX are likely dominant in solution at acidic pH, whereas most PPIXs are much less soluble. These oligomers are unlikely to bind BLG [43,89,90] and prompt significant photochemical mechanisms [76]. As a result, the ZnPPIX:BLG complex is a nearly negligible fraction (<3%) of the sample.…”

pH-tunable membrane-active polymers, NCMNP2a-x, and their potential membrane protein applications

“…S9B †) and its protonation state reduce the catalytic activity. 74,75 Low pH could result in protonation of the propionic moiety on PpIX, a decrease in the solubility of PpIX in the reaction system, and a signicant drop in its binding affinity to receptors. In conclusion, these results demonstrate the pH sensitivity of protoporphyrin IX breakdown by BcTSPO.…”

Kidney Involvement in Acute Hepatic Porphyrias: Pathophysiology and Diagnostic Implications

“…As a matter of fact, consistent pieces of evidence have been gathered concerning the cell-damaging effects of light-independent porphyrin-mediated toxicity [ 47 ]: in particular, intracellular, extralysosomal porphyrin accumulation engenders protein aggregation through noncovalent, oxygen-dependent, reversible mechanisms [ 48 , 49 ]. A particular susceptibility has been demonstrated, chiefly in hepatocytes, for intermediate filaments (nuclear laminins and cytoplasmatic keratins) [ 47 , 50 ], proteins in the endoplasmic reticulum (e.g., protein disulfide isomerase and calnexin) [ 51 ], proteasome regulatory particles, and key glycolytic enzymes, including glyceraldehyde 3-phosphate dehydrogenase [ 51 ].…”