SNCAIP

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title: "SNCAIP" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public topic_path: "uncategorized" source: "https://en.wikipedia.org/wiki/SNCAIP" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

Synphilin-1 is a protein that in humans is encoded by the SNCAIP gene. SNCAIP stands for "synuclein, alpha interacting protein".

Synphilin-1 is a cytosolic protein first identified in 1999 as a novel binding partner of α-synuclein, localized within Lewy bodies in Parkinson's disease brain tissue. Experimental studies in mammalian cells and yeast demonstrated that co-expression of synphilin-1 with α-synuclein promotes the formation of cytoplasmic inclusions resembling Lewy bodies.

Structure

The SNCAIP gene encodes synphilin-1, a multi-domain protein with a complex structure integral to neuronal function and implicated in neurodegenerative diseases. Structurally, synphilin-1 is composed of approximately 919 amino acids and is characterized by several functional domains, notably including six ankyrin repeats and a central coiled-coil domain spanning residues 510–557. These domains are typical protein-protein interaction motifs, facilitating synphilin-1's ability to interact with partner proteins such as alpha-synuclein (SNCA). SNCAIP binds to the N-terminal region of SNCA, allowing synphilin-1 to play a role in the formation of cytosolic inclusions mimicking Lewy bodies, which are hallmark features of synucleinopathies. The ankyrin repeats provide scaffolding for additional protein interactions, while the coiled-coil domain is crucial for the association with alpha-synuclein and possibly other synaptic or vesicular components.

Function

SNCAIP encodes synphilin-1, a cytoplasmic protein that interacts with alpha-synuclein in neuronal tissue and is involved in a variety of physiological processes related to synaptic function and protein homeostasis. Synphilin-1 is developmentally localized to synaptic terminals and participates in the regulation of synaptic vesicle trafficking. It may act as a scaffold protein, contributing to cellular processes like protein degradation through the ubiquitin-proteasome system and autophagy. Experimental evidence suggests that binding of synphilin-1 to alpha-synuclein can modulate synaptic vesicle dynamics, potentially impacting neurotransmitter release and synaptic plasticity. Synphilin-1's cytoprotective effects include inhibiting mitochondrial dysfunction, reducing reactive oxygen species production, and promoting neuronal survival under certain conditions.

Ubiquitination

Synphilin-1 undergoes ubiquitination. Parkin (an E3 ligase) modifies synphilin-1 and, together with α-synuclein, promotes the formation of ubiquitin-positive inclusion bodies. Mutations in parkin gene disrupt this activity. Additional E3 ligases, including SIAH1 and SIAH2, also ubiquitinate synphilin-1, influencing whether the protein is directed to proteasomal degradation or accumulates in inclusions. Inclusions containing α-synuclein and synphilin-1 share features with aggresomes, which may act to sequester misfolded proteins and limit cellular toxicity.

Clinical significance

Clinically, synphilin-1 is heavily implicated in neurodegenerative diseases, particularly Parkinson's disease (PD). It serves as a major component of Lewy bodies—the pathological protein aggregates characteristic of PD—and contributes to the formation of these cytoplasmic inclusions. While wild-type synphilin-1 may help sequester potentially toxic protein aggregates, certain isoforms and mutants, such as synphilin-1A, are highly aggregation-prone and associated with neuronal toxicity and degeneration. Genetic variation and altered methylation of the SNCAIP gene are linked with increased vulnerability to PD and related synucleinopathies. Thus, synphilin-1 exerts complex effects on neuronal health, acting as both a potential protector and a contributor to disease pathology depending on its expression, isoform, and interaction context.

Beyond Parkinson's disease, synphilin-1 has recently been implicated in glioblastoma. Transcriptomic and single-cell RNA sequencing analyses identified SNCAIP among histone lactylation related genes upregulated in glioblastoma, with elevated expression correlating with poorer patient survival. This has raised interest in synphilin-1 as a potential biomarker in cancer biology.

Interactions

SNCAIP has been shown to interact with:

References

References

  1. (May 1999). "Synphilin-1 associates with alpha-synuclein and promotes the formation of cytosolic inclusions". Nat Genet.
  2. "Entrez Gene: SNCAIP synuclein, alpha interacting protein (synphilin)".
  3. (May 1999). "Synphilin-1 associates with alpha-synuclein and promotes the formation of cytosolic inclusions". Nature Genetics.
  4. (April 2016). "The Parkinson Disease gene SNCA: Evolutionary and structural insights with pathological implication". Scientific Reports.
  5. "SNCAP_HUMAN".
  6. (Jun 2002). "Synphilin-1 is developmentally localized to synaptic terminals, and its association with synaptic vesicles is modulated by alpha-synuclein". Journal of Biological Chemistry.
  7. (Oct 2004). "The role of synphilin-1 in synaptic function and protein degradation". Cell Tissue Res..
  8. "Synphilin-1 and its Effects on Pathogenesis of Parkinson's Synphilin-1 and its Effects on Pathogenesis of Parkinson's Disease". University of Connecticut.
  9. (January 2019). "Synphilin-1 has neuroprotective effects on MPP+-induced Parkinson's disease model cells by inhibiting ROS production and apoptosis". Neuroscience Letters.
  10. (October 2001). "Parkin ubiquitinates the alpha-synuclein-interacting protein, synphilin-1: implications for Lewy-body formation in Parkinson disease". Nature Medicine.
  11. (April 2004). "Ubiquitylation of synphilin-1 and alpha-synuclein by SIAH and its presence in cellular inclusions and Lewy bodies imply a role in Parkinson's disease". Proceedings of the National Academy of Sciences of the United States of America.
  12. (February 2004). "Aggresomes formed by alpha-synuclein and synphilin-1 are cytoprotective". The Journal of Biological Chemistry.
  13. (April 2006). "Synphilin-1A: an aggregation-prone isoform of synphilin-1 that causes neuronal death and is present in aggregates from alpha-synucleinopathy patients". Proceedings of the National Academy of Sciences of the United States of America.
  14. (2023). "Parkinsonian phenotypes induced by Synphilin-1 expression are differentially contributed by serotonergic and dopaminergic circuits and suppressed by nicotine treatment". PLOS ONE.
  15. (June 2017). "Hypermethylation of Synphilin-1, Alpha-Synuclein-Interacting Protein (SNCAIP) Gene in the Cerebral Cortex of Patients with Sporadic Parkinson's Disease". Brain Sciences.
  16. (2025). "Identification and Validation of Prognostic Genes Related to Histone Lactylation Modification in Glioblastoma: An Integrated Analysis of Transcriptome and Single-cell RNA Sequencing". Journal of Cancer.
  17. (June 2002). "Analysis of synphilin-1 and synuclein interactions by yeast two-hybrid beta-galactosidase liquid assay". Neurosci. Lett..
  18. (Dec 2001). "Lack of binding observed between human alpha-synuclein and Bcl-2 protein family". Neurosci. Lett..
  19. (May 2001). "Interaction of alpha-synuclein and synphilin-1: effect of Parkinson's disease-associated mutations". J. Neurochem..
  20. (October 2001). "Parkin ubiquitinates the alpha-synuclein-interacting protein, synphilin-1: implications for Lewy-body formation in Parkinson disease". Nat. Med..

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