Formation of Lipofuscin-Like Autofluorescent Materials in NG108-15 Cells: Involvement of Lysosomal Protein Degradation

Abstract

We found that neuroblastoma × glioma hybrid NG108-15 cells accumulated lipofuscin-like autofluorescent materials during neuronal differentiation in culture in a medium containing 1% fetal calf serum, 1 mM dibutyryl cyclic AMP and 1 mM theophylline. The emission maximum of the lipofuscin-like autofluorescent materials was between 500 and 550 nm. Granules positive to acid phosphatase and periodic-acid Schiff were increased, as were the autofluorescent granules in NG108-15 cells. Thiolprotease inhibitors, N-(L-3-trans-carboxyoxirane-2-carbonyl)-L-leucine-4-aminobutylamide (E-64) and acetyl-Leu-Leu-Arg (leupeptin), markedly accelerated the accumulation of the lipofuscin-like autofluorescent materials in NG108-15 cells. On the other hand, activities of lysosomal thiolproteases, cathepsin B, C and L, were increased during neuronal differentiation. Protein content in the cells was gradually increased with the neuronal differentiation, and the rise was significantly accelerated when proteolysis was inhibited by E-64. These results suggest that the lipofuscin-like autofluorescent materials contain peptidic substances as a component, and indicate that the increase in hydrolytic activities of thiolproteases during neuronal differentiation is not enough for the hydrolysis of peptidic substrates, resulting in the accumulation of autofluorescent materials in NG108-15 cells.

GLUT-3 expression in human skeletal muscle

“…2 was labeled with FITC, and the resulting fluorescence was photographed using a Nikon Optiphot scope. The points of bright fluorescence in the control section (B) may be from lysosomes or lipofuscin autofluorescence (25). Figure 2A shows that all muscle fibers are positive for GLUT-3 protein, but a substantial number have a much lower signal.…”

Label-free monitoring of colorectal adenoma–carcinoma sequence based on multiphoton microscopy

“…According to previous publications, the TPEF of epithelial cells within the crypt is mainly determined by nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate (NADH and NADPH, NAD(P)H). The TPEF of cells within the interstitial space most likely was owing to flavin adenine dinucleotide (FAD) and other flavin proteins, and possibly lipofuscin [15,16]. In figure 1(b), a thin green band with uniform size and a honeycomb regular arrangement of round shape was clearly discerned, which originated from SHG signals of collagen fiber in the layer of lamina propria.…”