Cyclophilin D binds to the acidic C-terminus region of α-Synuclein and affects its aggregation characteristics

Abstract

cyclophilin D (cypD) is a peptidyl-prolyl isomerase expressed in the nucleus and transported into the mitochondria where it is best associated with the regulation of the mitochondrial permeability transition pore (Mptp). there are, however, other possible roles of cypD in the mitochondria which may or may not be linked with the Mptp. Alpha synuclein (αSyn) is shown here to interact directly with cypD via its acidic proline-rich c-terminus region and binding at the putative ligand binding pocket of cypD. the study shows that cypD binding with soluble αSyn prevents its aggregation. furthermore, the addition of cypD to preformed αSyn fibrils leads to the disassembly of these fibrils. Enzymaticallycompromised mutants of cypD show reduced abilities to dissociate αSyn aggregates, suggesting that fibril disassembly is linked to the increased rate of peptidyl-prolyl isomerisation catalysed by CypD. protein aggregation in the mitochondria is increasingly seen as the cause of neurodegeneration. However, protein aggregation is a reversible process but disaggregation requires help from other proteins such as isomerases and chaperones. the results here demonstrate a possible mechanism by which cypD achieves this and suggest that disaggregation could be one of the many functions of this protein. Cyclophilin D (CypD) is a mitochondrial peptidyl-prolyl isomerase that has been implicated to be involved in the mechanisms of many diseases, although it is best known as a regulator for the opening of the mitochondria permeability transition pore (MPTP). These conclusions were drawn from outcomes observed in in vivo studies involving the use of the potent inhibitor, cyclosporine A (CsA), and ppif gene knockdown mice 1,2. In a recent study, genetic ablation of CypD resulted in a delayed onset of Parkinson's Disease (PD) and extended lifespan of PD mice 3. Co-immunoprecipitation experiments in the same study show very weak direct interactions between CypD and αSyn 3. The connection between CypD and PD has not been clearly established, with the exception that mitochondrial dysfunction is a hallmark of PD 4. PD is characterised by the formation of Lewy bodies, which are protein aggregates containing the protein alpha-synuclein (αSyn) and selective degeneration of dopaminergic neurons in the substantia nigra brain region 5,6. Genome-wide analyses place mutations in SNCA, the gene encoding αSyn, as the top risk factor for those developing sporadic forms of the disease 7,8. αSyn redistributes from the cytoplasm to the outer and inner mitochondrial membrane with increased accumulation in PD 9,10. There is a correlation between αSyn entry into the mitochondria, reduced mitochondrial membrane potential (∆Ψ m) and mitochondria dysfunction, implicating the involvement of the MPTP 11,12. These effects of αSyn can be rescued by the addition of CsA, a CypD inhibitor, although this could be through the role of CypD as a regulator of the MPTP rather than as a result of direct interaction between αSyn and CypD 13. Proteins currently known to dissociate...

Peptidyl Prolyl Isomerase A Modulates the Liquid–Liquid Phase Separation of Proline-Rich IDPs

“…In order to gain further insights into the PPIA/tau interaction, we titrated 15 N-labeled PPIA with unlabeled tau. Only at very high molar excess of tau over PPIA did we detect Concentration of PPIA inside tau droplets.…”

“…Peptidyl prolyl isomerases are cotranslational chaperones that assist in the folding of nascent amino acid chains. − Their chaperoning activity in protein folding is associated with the cis/trans-interconversion of prolines, the only amino acid that can exist in both conformations. ,, Apart from their function in protein folding, prolyl isomerases, through the combination of their binding and isomerase activity, are associated with higher order assembly formation of IDPs, particularly the disease-associated misfolding of IDPs into amyloid fibrils: prolyl isomerases such as FK506-binding proteins, cyclophilin A, and cyclophilin D modulate the amyloid fibril formation of proline-rich IDPs associated with neurodegeneration including tau and α-synuclein. − In contrast to the regulatory activity of prolyl isomerases on the fibril formation of IDPs, their regulatory role on the LLPS behavior of IDPs is unknown.…”

The mitochondrial permeability transition pore: an evolving concept critical for cell life and death

“…CypD then remained the only protein whose involvement in the mPTP was uncontested: experiments performed with transgenic mice lacking the peptidylprolyl isomerase f (Ppif ) gene confirmed that this protein is a key element of the mPTP that is responsible for its sensitivity to Cyclosporin A (Basso et al, 2005;Valasani et al, 2014Valasani et al, , 2016Lindblom et al, 2020;Torpey et al, 2020;Panel et al, 2021). However, it should be stressed that CypD plays a regulatory role and is not involved in the pore itself (Fayaz, Raj & Krishnamurthy, 2015).…”

α-Synuclein-mediated neurodegeneration in Dementia with Lewy bodies: the pathobiology of a paradox

“…Owing to its higher proportion of charged residues and low hydrophobicity, it is conceivable that this domain undergoes specific phosphorylation at discrete sites [ 188 , 189 ] and is responsible for the intrinsically unstructured topology of α-synuclein. As radical as it may seem, there is now compelling evidence that the obliteration of C terminus, in tandem with alterations to the domain hydrophobicity, may possibly compromise the membrane-binding machinery and enhance the aggregation propensity of α-synuclein [ 190 – 195 ].…”