Biology subjects

Witt, S. N.

Publications and source records attributed to Witt, S. N..

5 recordsLinked to original sources

bioRxiv2025

Alpha-synuclein modulates the positioning of endolysosomes in melanoma cells

The Parkinsons disease-associated protein, alpha-synuclein (-syn; SNCA) is suspected of promoting melanoma progression. We recently knocked out SNCA in the human cutaneous melanoma cell line SK-MEL-28 to try to deduce the role of -syn in melanoma progression. Compared to control cells, the SK-MEL-28 SNCA-knockout (KO) cells have significantly inhibited growth, invasion, and migration, and the levels of the neural adhesion protein L1CAM and the transferrin receptor (TFR1) are significantly reduced. In this study, using transmission electron microscopy and immunofluorescence we show that SK-MEL-28 SNCA-KO cells relative to control cells exhibit an increased density of endolysosomes; increased perinuclear positioning of large (> 800 nm) endolysosomes; and decreased levels of the tetraspanins CD9 and CD81. Based on these results, we infer that -syn disrupts the balance between anterograde and retrograde traffic; thus, we propose that -syn is an accessory factor that that positively modulates the anterograde transport of endolysosomes and that loss of -syn expression results events (i)-(iii). We infer that low levels of L1CAM and CD81 (and other membrane proteins) are likely the underlying reason for the significantly reduced invasiveness and migratory properties of SK-MEL-28 SNCA-KO cells.

cancer biology↗

bioRxiv2024

Possible regulation of the immune modulator tetraspanin CD81 by alpha-synuclein in melanoma

We probed the mechanism by which the Parkinsons disease-associated protein -synuclein (-syn)/SNCA promotes the pathogenesis and progression of melanoma. We found that the human melanoma cell line SK-MEL-28 in which SNCA is knocked out (SNCA-KO) has low levels of tetraspanin CD81, which is a cell-surface protein that promotes invasion, migration, and immune suppression. Analyzing data from the Cancer Genome Atlas, we show that SNCA and CD81 mRNA levels are positively correlated in melanoma; melanoma survival is inversely related to the levels of SNCA and CD81; and SNCA/CD81 are inversely related to the expression of key cytokine genes (IL12A, IL12B, IFN, IFNG, PRF1 and GZMB) for immune activation and immune cell-mediated killing of melanoma cells. We propose that high levels of -syn and CD81 in melanoma and in immune cells drive invasion and migration and in parallel cause an immunosuppressive microenvironment; these contributing factors lead to aggressive melanomas. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=163 SRC="FIGDIR/small/593218v2_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@17513d4org.highwire.dtl.DTLVardef@168d161org.highwire.dtl.DTLVardef@8a4970org.highwire.dtl.DTLVardef@db7409_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2024

Alpha-synuclein regulates nucleolar DNA double-strand break repair in melanoma

Although an increased risk of the skin cancer melanoma in people with Parkinsons Disease (PD) has been shown in multiple studies, the mechanisms involved are poorly understood, but increased expression of the PD-associated protein alpha-synuclein (Syn) in melanoma cells may be important. Our previous work suggests that Syn can facilitate DNA double-strand break (DSB) repair, promoting genomic stability. We now show that Syn is preferentially enriched within the nucleolus in the SK-MEL28 melanoma cell line, where it colocalizes with DNA damage markers and DSBs. Inducing DSBs specifically within nucleolar ribosomal DNA (rDNA) increases Syn levels near sites of damage. Syn knockout increases DNA damage within the nucleolus at baseline, after specific rDNA DSB induction, and prolongs the rate of recovery from this induced damage. Syn is important downstream of ATM signaling to facilitate 53BP1 recruitment to DSBs, reducing micronuclei formation and promoting cellular proliferation, migration, and invasion.

cell biology↗

bioRxiv2023

Transcriptomic analysis of melanoma cells reveals an association of α-synuclein with regulation of the inflammatory response.

The Parkinsons disease protein, alpha-synuclein (-syn/SNCA), is highly expressed in neurons and melanomas. The goal of this study was to reveal the mechanism(s) of -syns involvement in melanoma pathogenesis. To decipher the genes and pathways affected by -syn, we conducted an RNA sequencing analysis of human SK-MEL-28 cells and several SK-MEL-28 SNCA-KO clones. We identified 1098 significantly up-regulated genes and 660 significantly down-regulated genes. Several of the upregulated genes are related to the immune system, i.e., the inflammatory response and the matrisome. We validated five upregulated genes (IL-1y, SAA1, IGFBP5, CXCL8, and CXCL10) by RT-qPCR and detected IGFBP5 and IL-1y in spent media of control and SNCA-KO cells. The levels of each of these secreted proteins were significantly higher in the spent media of the SNCA-KO clones than control cells. We suggest that the loss of -syn expression unleashes chemokine/cytokine secretion, which could help melanoma cells evade the immune system.

cancer biology↗

bioRxiv2023

Knocking out alpha-synuclein in melanoma cells downregulates L1CAM and decreases motility

The Parkinsons disease (PD) associated protein, alpha-synuclein (-syn/SNCA), is highly expressed in aggressive melanomas, which raises the possibility that -syn has a pro-survival function in melanoma. Herein, we asked whether -syn modulates the expression of the pro-oncogenic adhesion molecules L1CAM and N-cadherin. We used two human melanoma cell lines (SK-MEL-28, SK-MEL-29), SNCA-knockout (KO) clones, and two human SH-SY5Y neuroblastoma cell lines. In the melanoma lines, loss of -syn expression resulted in significant decreases in the expression of L1CAM and N-cadherin and concomitant significant decreases in motility. On average, there was a 75% reduction in motility in the four SNCA-KOs tested compared to control cells. Strikingly, comparing neuroblastoma SH-SY5Y cells that have no detectable -syn to SH-SY5Y cells that stably express -syn (SH/+S), we found that expressing -syn increased L1CAM and single-cell motility by 54% and 597%, respectively. The reduction in L1CAM level in SNCA-KO clones was not due to a transcriptional effect, rather we found that L1CAM is more efficiently degraded in the lysosome in SNCA-KO clones than in control cells. We propose that -syn is pro-survival to melanoma (and possibly neuroblastoma) because it promotes the intracellular trafficking of L1CAM.

cancer biology↗