Rapid formation of peptide/lipid co-aggregates by the amyloidogenic seminal peptide PAP_248-286

Abstract

5Protein/lipid co-assembly is an understudied phenomenon that is important to the function of antimicrobial peptides as 6 well as the pathological effects of amyloid. Here we study the co-assembly process of PAP 248-286 , a seminal peptide that 7 displays both amyloid-forming and antimicrobial activity. PAP 248-286 is a fragment of prostatic acid phosphatase and has 8 been reported to form amyloid fibrils, known as semen-derived enhancer of viral infection (SEVI), that enhance the viral 9 infectivity of HIV. We find that in addition to forming amyloid, PAP 248-286 much more readily assembles with lipid 10 vesicles into peptide/lipid co-aggregates that resemble amyloid fibrils in some important ways but are a distinct species. 11The formation of these co-aggregates, which we term "messicles", is controlled by the peptide:lipid (P:L) ratio and by the 12 lipid composition. The optimal P:L ratio is around 1:10 and at least 70% anionic lipid is required for co-aggregate 13 formation. Once formed, messicles are not disrupted by subsequent changes in P:L ratio. We propose that messicles form 14 through a polyvalent assembly mechanism, where a critical surface density of PAP 248-286 on liposomes enables peptide-15 mediated particle bridging into larger species. Even at ~100-fold lower PAP 248-286 concentrations, messicles form at least 16 10-fold faster than amyloid fibrils. It is therefore possible that, some or all of the biological activities assigned to SEVI, 17 the amyloid form of PAP 248-286 , could instead be attributed to a PAP 248-286 /lipid co-aggregate. More broadly speaking, this 18 work provides a potential framework for the discovery and characterization of peptide/lipid co-aggregates by other 19 amyloid-forming proteins and antimicrobial peptides. 20 Statement of Significance 21PAP 248-286 , a fragment of prostatic acid phosphatase, forms amyloid thought to enhances the infectivity of many 22 viruses, including HIV. This amyloid, termed semen-derived enhancer of viral infection (SEVI), has been assigned 23 responsibility for all of PAP 248-286 's biological activities, while the monomer is thought to be inactive. However, SEVI 24 formation is quite slow and requires very high concentrations of PAP . Here, we show that PAP 248-286 can instead 25 assemble much more rapidly with lipid membranes to form another species, mechanistically and morphologically distinct 26 from both monomer and SEVI amyloid. We have characterized this new species, which could play a role in the biological 27 activities currently ascribed to SEVI. Additionally, our proposed mechanism for peptide/lipid co-assembly could apply to 28 other biologically important systems. 29 30 Vane et al. PAP 248-286 /lipid co-aggregates 31Protein self-assembly has been important area of study for the past century. It is ubiquitous in biology -essential for 32 normal function and yet also underlying major diseases. Structural filaments like actin and tubulin microtubules, whose 33 assembly is critical for proper cellular motility, morphology, and trans...

Early Stages of Misfolding of PAP248-286 at two different pH values: An Insight from Molecular Dynamics Simulations

“…PAP248-286 peptides aggregate and form amyloid fibrils termed Semen-derived enhancers of viral infection (SEVI). The highly cationic nature of the SEVI fibrils facilitates their binding to the anionic membranes of HIV virions and cells, which leads to an increase in virion cell attachment and fusion 9,10,11 . In the recent times, several different approaches have been taken to reduce the PAP248-286-mediated rate of HIV infection.…”