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Alpha- and Gamma-Synuclein Proteins Define Complementary Metabolic and Invasive Programs in Melanoma Development, Progression, and Prognosis

This study reveals that alpha- and gamma-synuclein define complementary, anti-correlated malignant states in melanoma, where alpha-synuclein drives a metabolic program linked to mitochondrial function and gamma-synuclein promotes an invasive program via integrin-FAK-MAPK signaling, with high gamma-synuclein expression serving as a prognostic biomarker for poor outcomes.

Original authors: Mauricio Menacho Marquez, Florencia Malizia, Lucía Zanotti, Mirco Mian, Pablo Martínez Ponce, Macarena Mamberto, Aylén Avila, Nahuel Cesatti Laluce, Cecilia Farré, Andrés Binolfi, Xosé Bustelo, Lucian

Published 2026-10-29

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Mauricio Menacho Marquez, Florencia Malizia, Lucía Zanotti, Mirco Mian, Pablo Martínez Ponce, Macarena Mamberto, Aylén Avila, Nahuel Cesatti Laluce, Cecilia Farré, Andrés Binolfi, Xosé Bustelo, Luciano Anselmino

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ⚕️ This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer

Skin cancer, specifically a type called melanoma, is one of the most dangerous forms of the disease because it spreads quickly and often resists treatment. For decades, scientists have focused on the genetic mutations that drive these tumors, but a new study suggests that the behavior of these cancer cells is also controlled by a pair of proteins that are better known for their role in brain disorders. These proteins, called alpha-synuclein and gamma-synuclein, are usually found in nerve cells, where they help manage communication between neurons. When they malfunction in the brain, they clump together and cause Parkinson's disease. However, researchers have discovered that these same proteins are active in melanoma, where they do not act as a team but rather as opposing forces that push the cancer in two very different directions.

A team of scientists from Argentina and Spain set out to understand how these two proteins influence the life and death of melanoma cells. They found that the proteins define two distinct states for the cancer. One protein, alpha-synuclein, keeps the cancer cells in a state that is more like their original skin-cell identity. These cells are busy producing energy and pigment, much like healthy skin cells do. The other protein, gamma-synuclein, pushes the cells into a dangerous, aggressive mode. In this state, the cancer cells stop making pigment, become highly mobile, and develop the ability to invade surrounding tissues and resist standard chemotherapy drugs. The study reveals that these two proteins are rarely found at high levels in the same cell at the same time; instead, they act like a switch, with one rising as the other falls, determining whether the tumor remains relatively contained or becomes a spreading threat.

To reach these conclusions, the researchers examined a vast amount of data from patients with melanoma, looking at both the genetic instructions inside the cells and the actual proteins they produced. They analyzed samples from thousands of patients and looked at individual cells to see exactly where these proteins were located. They discovered that alpha-synuclein is mostly found in cells that are still acting like normal skin cells, while gamma-synuclein is concentrated in cells that have lost their skin-like features and are ready to move. This pattern held true across different groups of patients and even in the laboratory, where the scientists grew cancer cells in dishes. When they looked at the cells under a microscope, they saw that the presence of gamma-synuclein was linked to cells that were changing shape, becoming more elongated, and ready to travel.

The team then tested what happens when they changed the levels of these proteins in the lab. When they reduced the amount of alpha-synuclein, the cancer cells struggled to produce energy and lost their ability to make pigment. Conversely, when they reduced gamma-synuclein, the cells became less aggressive and, surprisingly, became more sensitive to cancer drugs. This suggests that gamma-synuclein is a key factor in helping the cancer survive treatment. The researchers also found that these proteins can be passed from one cell to another, similar to how a signal is transmitted in the brain. When they added these proteins from the outside to the cancer cells, the cells absorbed them and immediately became more active, growing faster and moving more quickly. This indicates that the cancer cells can use these proteins from their environment to boost their own survival and spread.

Perhaps the most significant finding relates to how these proteins affect the patient's future. The researchers looked at clinical records to see if the levels of these proteins could predict how a patient would do. They found that high levels of alpha-synuclein were generally linked to a poorer outcome, but the story was more complex for gamma-synuclein. In a specific group of patients with advanced-stage disease, those with high levels of gamma-synuclein had a much shorter time before their cancer returned or spread compared to those with low levels. This suggests that gamma-synuclein could serve as a warning sign for doctors, helping them identify patients who are at the highest risk of the cancer becoming aggressive and resistant to treatment.

The study also explored the inner workings of the cells to understand why these proteins have such different effects. They found that alpha-synuclein is tightly connected to the cell's power plants, known as mitochondria. Cells with high levels of this protein are very active in producing energy, but this activity makes them vulnerable to certain types of stress. On the other hand, gamma-synuclein is connected to a different set of signals that control how the cell moves and attaches to other structures. It turns on a pathway that helps the cell break down barriers and move through the body, while simultaneously turning down the signals that would normally make the cell sensitive to chemotherapy. This creates a state where the cancer is not just growing, but is actively hiding from the treatments designed to kill it.

This research changes the way scientists might think about treating melanoma. Instead of just trying to kill the cancer cells, the findings suggest that doctors might be able to change the behavior of the cells by targeting these proteins. If a treatment could lower the levels of gamma-synuclein, it might force the aggressive cancer cells to become less mobile and more sensitive to drugs. Alternatively, understanding how cancer cells absorb these proteins from their surroundings could open new doors for blocking their ability to spread. The study does not offer a new cure today, but it provides a clear map of the molecular switches that control whether melanoma stays put or goes on the attack. By identifying these specific proteins, the researchers have given the medical community new tools to better predict the course of the disease and potentially develop more effective strategies to stop it.

Technical Summary: Alpha- and Gamma-Synuclein Proteins Define Complementary Metabolic and Invasive Programs in Melanoma

Problem Statement
Melanoma remains a critical clinical challenge due to its metastatic potential and resistance to therapies. While synuclein proteins (specifically alpha-synuclein, $\alpha$ S, and gamma-synuclein, $\gamma$ S) are well-characterized in neurodegenerative contexts like Parkinson's disease, their roles in melanoma biology are less defined. Previous studies suggest $\alpha$ S promotes proliferation and invasion, while $\gamma$ S is linked to invasive behavior in other cancers. However, fundamental questions remain unresolved: whether SNCA and SNCG are co-regulated or mark distinct cell states, how they mechanistically contribute to tumor behavior, and if their expression identifies specific malignant subpopulations with adverse outcomes. This study aims to characterize the distinct contributions of $\alpha$ S and $\gamma$ S to melanoma development, progression, and prognosis by linking population-level transcriptomic associations with functional validation.

Methodology
The authors employed a multi-modal approach integrating bioinformatics, in vitro functional assays, and in vivo models:

Bioinformatics & Transcriptomics: The study analyzed multiple independent cohorts, including TCGA-SKCM, GTEx, and GSE datasets (GSE130973, GSE115978, GSE72056, GSE65904). Techniques included differential expression analysis, Gene Set Enrichment Analysis (GSEA), single-sample GSEA (ssGSEA) for metabolic and plasticity signatures, and single-cell RNA sequencing (scRNA-seq) to resolve cell-type-specific expression. Correlation analyses (Spearman/Pearson) were used to assess relationships between synucleins and transcriptional states (e.g., MITF, OXPHOS, EMT). Mediation analysis was performed to determine if MITF acts as a mediator between synuclein expression and downstream phenotypes.
Proteomics: Protein expression was evaluated using two public melanoma proteomic datasets (PXD026086 and PXD035206) to correlate transcript and protein levels.
Cell Biology & Molecular Mechanisms: Human (A375, SK-MEL-28) and murine (B16-F0, B16-F10) melanoma cell lines were used. The authors utilized shRNA-mediated silencing and plasmid-driven overexpression to modulate $\alpha$ $α$ S and $\gamma$ $γ$ S levels. Functional assays included:
- Proliferation (MTT, clonogenicity, cell counting).
- Migration and invasion (wound healing, transwell assays, Matrigel invasion).
- Signaling analysis (Western blotting for FAK, Rac1-GTP, $\beta$ -catenin, p-ERK, and qRT-PCR for MAP2K1).
- Mitochondrial bioenergetics (MTT reduction, mitochondrial membrane potential, MitoSOX for superoxide, and ROS assays).
- Drug sensitivity testing against cisplatin, vemurafenib, and paclitaxel.
Exogenous Protein Uptake: Recombinant $\alpha$ S and $\gamma$ S were purified, aggregated into oligomers and fibrils, and applied to cells to assess prion-like uptake and its functional consequences.
In Vivo Models: Syngeneic mouse models (B16-F0/F10) were used for subcutaneous allografts, spontaneous metastasis (post-surgical excision), and experimental metastasis (intrasplenic injection) to evaluate tumor growth and metastatic burden.

Key Contributions and Results

Reciprocal Expression and Cell State Definition:
- SNCA and SNCG exhibit a robust, inverse correlation across independent transcriptomic and proteomic cohorts, including at single-cell resolution.
- SNCA is predominantly expressed in malignant melanocytes, whereas SNCG is enriched in endothelial cells but also defines a specific, dedifferentiated subpopulation of malignant cells.
- High SNCA expression correlates with a differentiated, melanocytic state, while high SNCG expression correlates with a dedifferentiated, invasive, mesenchymal-like state.
Distinct Molecular Mechanisms:
- $\alpha$ S (Metabolic Program): $\alpha$ S is transcriptionally coupled to a MITF-linked program. It supports a metabolic state characterized by upregulated oxidative phosphorylation (OXPHOS) and melanogenesis. Functionally, endogenous $\alpha$ S acts as a "rheostat" that sensitizes mitochondrial Complex I to stress; its depletion improves basal mitochondrial bioenergetics and confers resilience to respiratory challenges (e.g., metformin).
- $\gamma$ S (Invasive Program): $\gamma$ S drives an invasive state via an integrin-FAK-Rac1-MAPK signaling axis. It sustains active Rac1-GTP, FAK autophosphorylation, and MAP2K1 (MEK1) transcription, while downregulating $\beta$ -catenin. This program is associated with reduced MITF expression and a dedifferentiated phenotype.
Prion-like Propagation and Drug Resistance:
- Melanoma cells actively internalize extracellular $\alpha$ S and $\gamma$ S in a prion-like manner. Unlike neuronal cells, which suffer toxicity from aggregated $\alpha$ S, melanoma cells utilize exogenous synucleins to enhance proliferation, clonogenicity, and migration.
- Silencing of $\gamma$ S confers cross-resistance to three mechanistically distinct therapeutic agents: cisplatin, vemurafenib, and paclitaxel. This suggests $\gamma$ S drives a "persister" or slow-cycling state that tolerates diverse therapies.
Clinical Prognosis:
- While high SNCA is associated with poorer overall survival in the general TCGA-SKCM cohort, high SNCG expression specifically identifies a subgroup of patients with Stage IIC melanoma who have a significantly shorter progression-free interval (PFI).
- The SNCG-high malignant subpopulation is defined by low MITF, high plasticity markers (e.g., AXL, ZEB1), and is associated with stromal and immune remodeling.

Significance and Claims
The paper claims to establish $\alpha$ S and $\gamma$ S as functionally distinct, mechanistically convergent regulators of a "metabolic-versus-invasive" cell-state dichotomy in melanoma. The authors posit that these paralogs are not redundant but define complementary programs that converge on the master MITF differentiation axis from opposite directions:

$\alpha$ S maintains a metabolically active, differentiated state that is vulnerable to metabolic stress.
$\gamma$ S drives a dedifferentiated, invasive, and drug-tolerant state.

The study nominates SNCG as a candidate prognostic biomarker for Stage IIC melanoma and identifies Complex I sensitization (via $\alpha$ S) and FAK/MAPK signaling (via $\gamma$ S) as potential therapeutic vulnerabilities. The authors emphasize that the balance between these synuclein paralogs may govern the plasticity underlying melanoma progression, offering a new framework for understanding phenotype switching and drug resistance. They modestly note that while SNCG is a promising biomarker, its prognostic value in Stage IIC requires validation in larger, independent cohorts, and the mechanistic links (e.g., direct causality in the $\gamma$ S-FAK-MAPK axis) await further epistatic or pharmacological validation.

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