뇌척수액 지단백질은 α를 억제합니다.

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May 14, 2024

뇌척수액 지단백질은 α를 억제합니다.

분자 신경변성 18권, 기사 번호: 20(2023) 이 기사 인용 1885 액세스 3 인용 21 Altmetric Metrics 세부 정보 α-시누클레인(α-syn)의 응집은 다음의 두드러진 특징입니다.

분자 신경변성 18권, 기사 번호: 20(2023) 이 기사 인용

1885년 접속

3 인용

21 알트메트릭

측정항목 세부정보

α-시누클레인(α-syn)의 응집은 파킨슨병(PD) 및 기타 시누클레인병증의 두드러진 특징입니다. 현재 뇌척수액(CSF)을 사용한 α-syn 시드 증폭 분석(SAA)은 시누클레인병증에 대한 가장 유망한 진단 도구입니다. 그러나 CSF 자체에는 환자 의존적 방식으로 α-syn의 응집을 조절할 수 있는 여러 화합물이 포함되어 있어 잠재적으로 최적화되지 않은 α-syn SAA를 약화시키고 종자 정량화를 방지합니다.

본 연구에서 우리는 CSF 분획화, 질량 분석법, 면역 분석, 투과 전자 현미경, 용액 핵 자기 공명 분광법, 매우 정확하고 표준화된 진단 SAA 및 다양한 방법을 사용하여 α-syn 응집체 검출에 대한 CSF 환경의 억제 효과를 특성화했습니다. α-syn의 자발적인 응집을 평가하기 위한 시험관 내 응집 조건.

우리는 CSF의 고분자량 분율(> 100,000 Da)이 α-syn 응집을 매우 억제하는 것으로 나타났으며 지단백질이 이 효과의 주요 동인임을 확인했습니다. 지질단백질과 단량체 α-syn 사이의 직접적인 상호작용은 용액 핵자기공명 분광법에 의해 검출되지 않았지만, 반면에 우리는 투과전자현미경으로 지질단백질-α-syn 복합체를 관찰했습니다. 이러한 관찰은 지질단백질과 올리고머/원섬유성 α-syn 중간체 사이의 상호작용을 가정하는 것과 호환됩니다. 우리는 지단백질이 진단 SAA의 반응 혼합물에 첨가되었을 때 PD CSF에서 α-syn 시드의 상당히 느린 증폭을 관찰했습니다. 또한, 우리는 ApoA1과 ApoE를 면역 고갈시킨 후 α-syn 응집에 대한 CSF의 억제 능력이 감소하는 것을 관찰했습니다. 마지막으로, 우리는 CSF ApoA1 및 ApoE 수준이 미리 형성된 α-syn 응집체로 스파이크된 n = 31 SAA 음성 대조군 CSF 샘플에서 SAA 운동 매개변수와 유의한 상관관계가 있음을 관찰했습니다.

우리의 결과는 α-syn 원섬유의 형성을 억제하고 관련 시사점을 가질 수 있는 지질단백질과 α-syn 응집체 사이의 새로운 상호 작용을 설명합니다. 실제로 α-syn 응집에 대한 기증자별 CSF 억제는 현재까지 SAA 유래 동역학 매개 변수 분석의 정량적 결과가 부족함을 설명합니다. 또한, 우리의 데이터는 지단백질이 CSF의 주요 억제 구성 요소임을 보여 주므로 지단백질 농도 측정이 데이터 분석 모델에 통합되어 α-syn 정량화 노력에 대한 CSF 환경의 교란 효과를 제거할 수 있음을 시사합니다.

파킨슨병(PD), 루이체 치매(DLB) 및 다계통 위축(MSA)은 취약한 뇌 영역에 세포내 α-syn 봉입체가 존재하는 병리학적 특징을 갖는 신경퇴행성 질환이며 일반적으로 시누클레인병증(synucleinopathy)이라고 합니다. 프리온 분야에서 단백질 미스폴딩 순환 증폭(PMCA)[1] 및 실시간 진동 유도 변환(RT-QuIC)[2]으로 알려진 시드 증폭 분석(SAA)은 최근 α-syn 응집체를 검출하는 데 적용되었습니다. 인간의 생물학적 체액과 조직에서 발견되며 가까운 미래에 시누클레인병증의 진단을 크게 향상시킬 수 있습니다. SAA는 생물학적 매트릭스에 존재하는 미량의 프리온 유사 α-syn 집합체(α-syn 종자)의 증폭을 기반으로 하며, 신장 및 단편화 주기를 통해 추가된 재조합 α-syn 단량체를 모집하여 시험관 내에서 전파됩니다[3, 4 ]. 증폭 과정은 아밀로이드 응집체의 교차 β-시트 모티프에 높은 친화력으로 결합하는 형광 염료인 티오플라빈-T(ThT)를 사용하여 모니터링됩니다. 놀랍게도, SAA는 전구성 PD 사례에서 CSF의 α-syn 시드를 검출하여[5, 6], 본격적인 질병이 있는 환자에서와 유사한 민감도에 도달했습니다[7,8,9]. 초기 보고서에서는 응집 속도와 질병 진행(H&Y 점수)[1] 및 CSF에 스파이크된 합성 α-syn 응집체 수준 사이의 상관관계를 보여주었습니다[1, 7]. 그러나 이러한 결과는 더 큰 집단을 분석할 때 재현되지 않았으며[9, 10], 연속 희석에 의한 반정량화도 질병 진행과 상관관계가 없었습니다[7, 9]. 건강한 대조군(HC)과 시누클레인병증 사례 모두에서 CSF가 단독 완충제와 비교하여 α-syn 응집을 억제하는 것으로 관찰되었습니다[1, 11,12,13]. 결과적으로 SAA 프로토콜에는 억제를 극복하고 α-syn 시드의 효율적인 증폭을 가능하게 하기 위해 CSF 희석이 포함됩니다[2, 11]. 이 효과는 반복적으로 관찰되었지만 놀랍게도 아직 특성화되지 않았습니다. 실제로, α-syn 응집에 대한 CSF의 효과는 질병 진행 및 α-syn 부담과 관련된 분석 매개변수 사이의 명백한 상관관계 부족을 설명할 수 있습니다[9, 10].

 2000, 0 < t1 < 100 h and t2 > 0. For some kinetic traces, a decrease in fluorescence was observed after reaching the second plateau. This known phenomenon is caused by the sequestration of ThT molecules by mature fibrils and by the sedimentation of HMW insoluble aggregates [21]. In these cases, the last descending part of the ThT profile was removed prior to fitting. Fitting was rejected when the adjusted determination coefficient R2 was below 0.3./p> 100 kDa), CSF constituents of MW between 100 and 50 kDa (100-50 kDa), CSF constituents of MW between 50 and 10 kDa (50-10 kDa), CSF constituents of MW between 10 and 3 kDa (10-3 kDa), and CSF constituents of MW below 3 kDa (< 3 kDa). We then analysed the inhibitory effect of each of these 6 fractions on the spontaneous aggregation of α-syn in the previously mentioned PBS conditions (i.e., those of Fig. 2B, C, E). There were clear differences in α-syn aggregation depending on the MW of the CSF fraction. Whole CSF and all the fractions with MW > 10 kDa drastically inhibited α-syn aggregation, while 10-3 kDa and < 3 kDa fractions showed comparable aggregation to the reaction without CSF components (PBS control) (Fig. 4B). We estimated the second fluorescence plateau (A2) using the double sigmoidal model and compared the results to the maximum fluorescence readings (Fmax) for all 6 CSF-derived samples (Fig. 4C). As expected, A2 and Fmax were very similar within each CSF derived sample, confirming the goodness of the fit, except for whole CSF and > 100 kDa for which fitting was not possible. Indeed, for whole CSF and > 100 kDa, fluorescence readings remained practically flat, impeding the fit through the double sigmoidal model. Suggesting lower inhibition of α-syn aggregation, A2 and Fmax were substantially higher in both 10–3 and < 3 kDa fractions, which were comparable to the PBS control. Some inhibition was observed in the < 3 kDa fraction, but this is probably the result of an increase in pH by air exposure during the fractionation procedure rather than an inhibition of α-syn aggregation by protein components (as described in Supplementary Material Solution NMR experiments on CSF fractions and Fig. S4-5). A2 and Fmax dropped significantly for 50–10 and 100–50 kDa fractions, consistent with a higher degree of α-syn aggregation inhibition, while whole CSF and > 100 kDa were the most inhibitory (Fig. 4C). Estimations of t2 show similar results, with whole CSF and > 100 kDa significantly slowing down aggregation (Supplementary Material Fig. S6). These results indicate that the main inhibitory components of CSF are enriched in the > 100 kDa fraction, which retained the same inhibitory effect as whole CSF. To identify protein candidates responsible for the inhibition of α-syn aggregation, we analysed the CSF derived samples by nLC-nESI HRMS/MS (Fig. 4D). We could not detect relevant amounts of proteins in the 10–3 kDa and < 3 kDa fractions by nLC-nESI HRMS/MS (just very low levels of albumin or albumin fragments in the 10-3 kDa fraction, see Supplementary Material, Table S2). In whole CSF, the most abundant of the ~ 300 proteins detected were albumin, transthyretin (TTR), apolipoproteins, and prostaglandin-D synthase (PGDS, also known as β-trace protein). Albumin and PGDS were found not particularly enriched in the > 100 kDa fraction, suggesting low inhibition effect of these two proteins on α-syn aggregation. Following the inhibitory effect on α-syn aggregation, apolipoproteins were more abundant in whole CSF and the > 100 kDa fraction. ApoA1 and ApoE were the most abundant apolipoproteins in the > 100 kDa fraction (~ 80%), while ApoJ and ApoD accounted for ~ 6% each. The higher abundance of fatty acids-rich lipoproteins and/or other HMW proteins in NPH1 vs NPH2, and the high abundance of lipoproteins in the most inhibitory fraction of CSF (> 100 kDa) suggest that these compounds in CSF could be the main driver of the inhibition of seeded and spontaneous aggregation of α-syn./p> 100 kDa fraction) and maximum fluorescence values (Fmax) estimated from individual ThT traces. Two scales of fluorescence intensity were used to better compare the results. Represented values correspond to the average of three replicates with error bars reflecting the SEM. D Relative concentration (emPAI score multiplied by protein molecular weight) of the most abundant protein constituents measured by nLC-nESI HRMS/MS. Apolipoproteins scores were summed together, with ApoA1 and ApoE being the most abundant (~ 85% of the total). Scores for fractions 10–3 and < 3 kDa are not shown since the protein content of these fractions was negligible with respect to the others/p> 100 kDa CSF fraction, we evaluated if HDL could retain the same level of inhibition when tested within a range of concentrations from 1 to 0.003 mg/mL (including the physiological ones of human CSF). Interestingly, we observed a dose-dependent partial inhibition of α-syn aggregation when adding 0.003 and 0.03 mg/mL, while 0.3 and 1 mg/mL completely blocked the formation of ThT-reactive aggregated species (Fig. 6A). The partial inhibition was most noticeable as a delay in the second inflection point (t2), although it was also observed as a reduction in fluorescence of the first plateau (A1) (Fig. 6A inset). ApoE and ApoA1 represent 50–60% of total CSF apolipoprotein, and their respective reported concentration in CSF is approximately 0.01 mg/mL and 0.004 mg/mL [26]. Considering 0.03 mg/mL as the physiological concentration of HDL in CSF, our results show that HDL partially inhibited α-syn aggregation at a physiological concentration and at a tenfold lower concentration. Although our experiments were performed with highly purified recombinant α-syn and other components were shown not to form ThT, OC, or A11 detectable aggregates, we used WB to detect monomeric recombinant α-syn as a secondary read-out for this experiment. In agreement with ThT readings, in the absence of HDL, there was a decrease in monomeric α-syn at the time of the first plateau (48 h) and most of the monomer was consumed by the time of the second plateau (180 h) (Fig. 6B, Supplementary Material Fig. S8A). However, we detected monomeric α-syn in the presence of HDL after 180 h of the reaction, with the monomer signal being found increased at increasing concentrations of HDL (highest at 1 mg/mL HDL and the lowest in absence of HDL, Fig. 6C). However, it is worth mentioning that, in the presence of 1 mg/mL HDL, we observed an additional band (around 150–200 kDa) of much lower intensity than the monomer band (Supplementary Material Fig. S8B-C), suggesting that high concentrations of HDL may have stabilised some prefibrillar oligomers, preventing their conversion into fibrils. Collectively, these results show that purified serum HDL (at physiological concentrations and in the absence of CSF milieu) is a potent inhibitor of α-syn aggregation, comparable to whole CSF and the > 100 kDa CSF fraction./p> 200 h t2). TTR did not inhibit α-syn spontaneous aggregation when tested within the physiological concentration range (0.03 and 0.3 mg/mL) (Fig. 7A-B). Nevertheless, TTR showed partial inhibition, most noticeable in Fmax/A2 when tested at 1 mg/mL, which has been reported to be near the plasma physiological concentration of TTR [29]. These results suggest that the size, density, or lipidic content of the lipoprotein are not critical for the inhibition of α-syn aggregation, although these factors may modulate the level of inhibition on α-syn aggregation./p> 100 kDa) retained the same inhibitory effect on α-syn aggregation as whole CSF, while fractions of smaller MW were less inhibitory. It should be considered that the pore size distribution of MWCO filters allows a low percentage of HMW components to pass through the filter in smaller MW fractions. This potential leak of HMW material into lower MW fractions could explain the lower but still detectable inhibitory effect observed in those fractions. Using MS we identified albumin, TTR, PGDS, and apolipoproteins to be the most abundant HMW components in the NC CSF pool used. The distribution of apolipoprotein in the CSF fractions correlated with the inhibition of each fraction on α-syn aggregation, while albumin, TTR, and PGDS did not. Apolipoproteins, particularly ApoA1 (28.3 kDa) and ApoE (34 kDa), were the most represented in the > 100 kDa fraction. Given the MW, these apolipoproteins were most likely assembled in lipoproteins in CSF. We then confirmed that serum-purified HDL in the absence of CSF milieu was able to inhibit α-syn spontaneous aggregation. Moreover, the partial inhibition was observed when evaluating HDL at CSF sub-physiological concentrations. These findings were confirmed by tracking the aggregation using dot blot with two different conformational antibodies and WB detecting the monomeric α-syn that was not converted into fibrils in the aggregation reaction. In these experiments, although most α-syn remained monomeric at 1 mg/mL HDL, we could spot the presence of a band at 150–200 kDa, suggesting that high HDL concentrations might have stabilised some prefibrillar oligomers, impeding their conversion into fibrils. Since CSF HDL are bigger in size than blood HDL and smaller than blood LDL [27, 28], we also evaluated the inhibitory effect of serum-purified LDL on α-syn aggregation and observed a similar or greater inhibitory effect than with HDL even at sub-physiological concentrations. We evaluated HDL and LDL at the same concentrations in terms of mg/mL, but because of the smaller molecular weight of HDL, molar concentration of HDL was greater than the concentration of LDL in our α-syn aggregation experiments. Thus, the higher inhibitory effect of LDL might indicate that the inhibition is driven by the lipidic fraction of the complex, although there are many reports showing that lipids promote aggregation of α-syn [31]./p>

100 kDa CSF fraction in PBS. The residues experiencing the largest decreases in signal intensity (smaller by one or more standard deviations with respect to the average value) are highlighted in light blue. The intensity ratios corresponding to overlapping peaks are highlighted in red (their values were not considered in the calculation of the average decreases and standard deviations). Fig. S5. CSF pH drift. The pH change due to the exposure of CSF to air was monitored over time in 500 μL of undiluted pooled CSF (A) and in the presence of PBS (400 μL CSF + 200 μL PBS 3x) in polypropylene vials with a Thermo Scientific Orion pH-meter equipped with a glass 6 mm diameter pHenomenal MIC 220 Micro electrode. Right before each measurement, the sample was vortexed for 20 sec and left open to air for another 20 sec. Fig. S6. Different CSF fractions differently affect α-syn aggregation. Mean fitted t2 parameters of samples with 40 μl of PBS/CSF fractions. The values displayed result from the average of three replicates with error bars reflecting the SEM. For whole CSF and the >100 kDa fraction the total duration of the experiment is shown due to the absence of appreciable aggregation. Fig. S7. Raw images of the dot-blot assays. A-B) Native images of the dot-blot assay performed on α-syn alone replicates at different timepoints with OC (A) and A11 (B) conformational antibodies. C-D) Native image of the dot-blot assay performed on the HSA and HDL containing samples with OC (C) and A11 (D) conformational antibodies. Fig. S8. WB experiments to track α-syn aggregation in the presence of human HDL. A) α-Syn aggregation patterns in samples collected at different timepoints of the spontaneous aggregation process, was monitored by WB using Syn211 antibody (4-20% SDS-PAGE, 2 μg protein loaded). Monomeric α-syn decreases as t increases due to the formation of fibrils. B) In a similar way, a WB with Syn211 was performed on the reaction products obtained after 180 h, at different HDL concentrations with and without α-syn (exposure time 210 s). C) The experiment was then repeated by doubling the amount of sample loaded into the gel to better highlight the presence of oligomeric species (exposure time 30 s). Under these conditions, chosen to better visualize the signal at 150-200 kDa, the α-syn monomer bands at 1 and 0.3 mg/mL HDL may not quantitively reflect monomer concentration (overloaded lanes). Fig. S9. Representative TEM images of α-syn incubated with CSF. Representative TEM images obtained by analyzing samples obtained by the co-incubation of α-syn 0.7 mg/mL at 37 °C with pooled human CSF (1:5 ratio with respect to total reaction volume). Samples were subjected to cycles of incubation (13 min) and shaking (double-orbital, 2 min) at 500 rpm. Fig. S10. NMR titrations of α-syn with HDL, LDL and TTR. A) Intensity decreases of the signals of two-dimensional (2D) 15N–1H HSQC experiments acquired at 950 MHz at T = 283 K on 15N labelled α-syn (100 μM) in PBS after the addition of 0.57 mg/mL serum-derived HDL. The intensity ratios corresponding to overlapping peaks are highlighted in red. B) Intensity decreases of the signals of two-dimensional (2D) 15N–1H HSQC experiments acquired at 950 MHz at T = 283 K on 15N labelled α-syn (100 μM) in PBS after the addition of 1 mg/mL serum-derived LDL. C) Intensity decreases of the signals of two-dimensional (2D) 15N–1H HSQC experiments acquired at 950 MHz at T = 283 K on 15N labelled α-syn (100 μM) in PBS after the addition of 3 mg/mL TTR. Fig. S11. WB experiments performed on immunodepleted CSF. WB experiments were performed with anti-ApoA1 (MIA1404) and anti-ApoE (PA5-27088) antibodies on neat CSF and supernatants (400 μL CSF, 100 μL slurry) resulting from immunoprecipitation procedure performed using different quantities of the same antibodies (IP CSF samples), immunoprecipitation performed without antibodies (CSF IP no Ab). The conditions relative to IP CSF ApoA1 60 µg and IP CSF ApoE 20 µg were then selected for Protein aggregation assays. Table S1. Concentration factors and final volumes of the CSF fractions./p>