Epigallocatechin-3-gallate rapidly remodels PAP85-120, SEM1(45-107), and SEM2(49-107) seminal amyloid fibrils

Abstract

Semen harbors amyloid fibrils formed by proteolytic fragments of prostatic acid phosphatase (PAP248-286 and PAP85-120) and semenogelins (SEM1 and SEM2) that potently enhance HIV infectivity. Amyloid but not soluble forms of these peptides enhance HIV infection. Thus, agents that remodel these amyloid fibrils could prevent HIV transmission. Here, we confirm that the green tea polyphenol, epigallocatechin-3-gallate (EGCG), slowly remodels fibrils formed by PAP248-286 termed SEVI (semen derived enhancer of viral infection) and also exerts a direct anti-viral effect. We elucidate for the first time that EGCG remodels PAP85-120, SEM1(45-107), and SEM2(49-107) fibrils more rapidly than SEVI fibrils. We establish EGCG as the first small molecule that can remodel all four classes of seminal amyloid. The combined anti-amyloid and anti-viral properties of EGCG could have utility in preventing HIV transmission.

Keywords: EGCG; HIV infectivity; PAP85-120; SEM1; SEM2; SEVI.

Fig. 1.

EGCG slowly remodels SEVI fibrils into non-amyloid structures. (A) Preformed SEVI fibrils (20 µM) were incubated with buffer or EGCG (200 µM) for 0–24 h. Fibril integrity was assessed by ThT fluorescence. Values represent means±s.e.m. (n=4). (B) Transmission electron micrographs of SEVI fibrils incubated with buffer or EGCG for 2 h or 24 h. Scale bar: 2 µm. (C) SEVI fibrils (20 µM) were incubated with buffer for 6 h or 24 h or EGCG (200 µM) for 6 h or 24 h, and the resulting products were used to seed soluble PAP248-286 (1 mM, 0.1% fibril seed) fibrillization. Buffer conditions lacking fibril seed were included. Fibril assembly was monitored by ThT fluorescence. Values represent means±s.e.m. (n=4). (D-F) Preformed SEVI fibrils (20 µM) were incubated with buffer or EGCG (200 µM) for 0–24 h. Fibril integrity was assessed by anti-amyloid (OC) immunoreactivity (D), turbidity (E), or sedimentation analysis (F). Values represent means±s.e.m. (n=3).

Fig. 2.

EGCG rapidly remodels PAP85-120 amyloid fibrils. (A-D) PAP85-120 fibrils (20 µM) were incubated with buffer or EGCG (200 µM) for 0−24 h. Fibril integrity was assessed by measuring: ThT fluorescence intensity (A), OC immunoreactivity (B), turbidity (C), or sedimentation analysis (D). Values represent means±s.e.m. (n=3). (E) Transmission electron micrographs of PAP85-120 fibrils incubated with buffer (untreated) or EGCG for 6 h. Scale bar: 500 nm.

Fig. 3.

EGCG rapidly remodels SEM1(45-107) fibrils. (A) SEM1(45-107) fibrils (20 µM) were incubated with buffer or EGCG (200 µM) for 0–24 h. Fibril integrity was assessed by measuring: ThT fluorescence intensity (A), OC immunoreactivity (B), turbidity (C), or sedimentation analysis (D). Values represent means±s.e.m. (n=3). (E) Transmission electron micrographs of SEM1(45-107) fibrils incubated with buffer or EGCG for 2 h. Scale bar: 500 nm.

Fig. 4.

EGCG rapidly remodels SEM2(49-107) fibrils. (A) SEM2(49-107) fibrils (20 µM) were incubated with buffer or EGCG (200 µM) for 0–24 h. Fibril integrity was assessed by measuring: ThT fluorescence intensity (A), OC immunoreactivity (B), turbidity (C), or sedimentation analysis (D). Values represent means±s.e.m. (n=3). (E) Transmission electron micrographs of SEM2(49-107) fibrils incubated with buffer or EGCG for 2 h. Scale bar: 500 nm.

Fig. 5.

EGCG inhibits HIV infectivity in cell culture. TZM-bl cells were infected with three HIV-1 strains (BL2, BaL, and 89.6) in the presence of the indicated concentrations of EGCG (final concentration in cell culture). Infectivity was monitored by measuring luciferase activity in the cell cultures. Values represent means±s.e.m. (n=3).