APOA4主要在肠道中转录和翻译，并通过循环运输到脂肪组织。(A) APOA4基因在小鼠空肠和肝脏组织中有表达，而在性腺脂肪组织和肾脏中无表达。RT-PCR检测129X1/SvJ WT雄性和雌性小鼠空肠、肝脏、性腺脂肪和肾脏组织中总mRNA的ApoA4和β-actin。ApoA4水平用β-肌动蛋白水平归一化，数据显示为空肠中归一化ApoA4 mRNA水平的折叠变化。参见补充图S1。(B) WT组织中存在APOA4蛋白，但APOA4−/−小鼠组织中不存在。用SDS-PAGE分离空肠、肝脏、附睾脂肪、肾脏组织和血浆中总蛋白(40 μg)，用抗apoa4抗体检测。将印迹剥离，用抗-β-肌动蛋白检测，进行负载控制和归一化。代表性的western blot图像显示，WT小鼠的所有组织中均存在APOA4蛋白，但不存在APOA4−/−小鼠(n = 3/组);这些发现也证实了所使用抗体的特异性。 (C-E) Representative immunofluorescence confocal images of APOA4 immunoreactivity (IR) in mouse gonadal fat tissues. Epididymal fat from male and periovarian fat from female mice were harvested, fixed, paraffin embedded, sectioned and stained with anti-APOA4 and anti-caveolin-1 (n = 2 technical and 3 biological replicates). Scale bar: 50 μm. (C) APOA4 immunoreactivity (APOA4-IR) was present at the cell surface of adipocytes in a discrete manner in male and female WT mice (arrows) and in the vasculature (inset: arrowhead), (D) no APOA4-IR was detected in ApoA4−/− mice, thereby also confirming specificity of the antibody used. (E) I.p. injection of r-m-APOA4 (5 μg/g body weight) in ApoA4−/− mice resulted in APOA4 uptake in gonadal fat tissues with similar pattern of localization of APOA4-IR in adipocytes as that in WT mice (arrows show discrete cell surface expression). (F) Apo-A-IV-IR co-localized with the adipocyte cell surface marker caveolin-1 (Merge, yellow arrows), but not in the vasculature (white arrowhead), confirming that exogenous APOA4 is targeted to the appropriate cell types. Scale bar: 50 μm and 10 µm. Credit: DOI: 10.1038/s41598-021-92711-0
