Time-Dependent Internalization of S100B by Mesenchymal Stem Cells via the Pathways of Clathrin- and Lipid Raft-Mediated Endocytosis

Abstract

Mesenchymal stem cells (MSCs) are promising tools for cancer therapy, but there is a risk of malignant transformation in their clinical application. Our previous work revealed that the paracrine protein S100B in the glioma microenvironment induces malignant transformation of MSCs and upregulates intracellular S100B, which could affect cell homeostasis by interfering with p53. The purpose of this study was to investigate whether extracellular S100B can be internalized by MSCs and the specific endocytic pathway involved in S100B internalization. By using real-time confocal microscopy and structured illumination microscopy (SIM), we visualized the uptake of fluorescently labeled S100B protein (S100B-Alexa488) and monitored the intracellular trafficking of internalized vesicles. The results showed that S100B-Alexa488 was efficiently internalized into MSCs in a time-dependent manner and transported through endolysosomal pathways. After that, we used chemical inhibitors and RNA interference approaches to investigate possible mechanisms involved in S100B-Alexa488 uptake. The internalization of S100B-Alexa488 was inhibited by pitstop-2 or dyngo-4a treatment or RNA-mediated silencing of clathrin or dynamin, and the lipid raft-mediated endocytosis inhibitors nystatin and MβCD. In conclusion, our findings show that clathrin and lipid rafts contribute to the internalization of S100B-Alexa488, which provides promising interventions for the safe application of MSCs in glioma therapy.

Biomembrane-wrapped gene delivery nanoparticles for cancer therapy

“…After ligand-receptor binding, targeting NPs enter tumor cells mainly through endocytosis-mediated internalization. Generally speaking, the standard internalization mode includes phagocytosis ( Butler and Popescu, 2021 ), clathrin-mediated endocytosis ( Moreno-Layseca and Jantti, 2021 ), caveolae-mediated endocytosis ( Nie et al, 2021 ), lipid raft-mediated endocytosis ( Zhang et al, 2021c ), micropinocytosis ( Zhang et al, 2022b ) ( Figure 2 ). Previous studies have shown that caveolin-mediated endocytosis can transport nucleic acids directly to the Golgi apparatus or endoplasmic reticulum via the endosome-golgi apparatus-endoplasmic reticulum pathway, thus avoiding degradation in lysosomes ( Wang et al, 2020a ).…”

How S100B crosses brain barriers and why it is considered a peripheral marker of brain injury

“…Despite the lack of available data, we should not exclude the possibility of renal protein absorption, since S100B could be internalized by clathrin- and lipid raft-mediated endocytosis. 97 In renal inflammatory processes, especially in diabetic patients and experimental models, there is an increase in RAGE, fibrosis, and AGEs accumulation. 98,99 However, this possibility of absorption in the proximal tubules of S100B needs further investigation.…”

GFAP and S100B: What You Always Wanted to Know and Never Dared to Ask

“…The presence in extracranial organs is due to the cellular uptake of circulating S100B ( 21 ) by a mechanism recently proposed in ref. ( 23 ) showing that clathrin and lipid rafts contribute to the internalization of S100B. The contribution of expression outside the CNS to the blood signal in a healthy individual is minor as the highest value, including all extracranial sources, is well below the levels seen in TBI ( 24 ).…”