| LITAF | |
|---|---|
| Gene Symbol | LITAF |
| Full Name | Lipopolysaccharide-Induced Tumor Necrosis Factor Factor |
| Chromosomal Location | 16p13.13 |
| NCBI Gene ID | 10868 |
| Ensembl ID | ENSG00000106789 |
| OMIM ID | 604577 |
| UniProt ID | Q9Y5K2 |
| Protein Alias | SIMPLE, CMT1C |
| Associated Diseases | Charcot-Marie-Tooth Disease Type 1C |
LITAF (Lipopolysaccharide-Induced Tumor Necrosis Factor Factor), also known as SIMPLE (Small Integral Membrane Protein of Lysosome/Late Endosome), is a gene encoding a 161-amino acid protein involved in cellular protein quality control, lysosomal trafficking, and inflammatory signaling. Located on chromosome 16p13.13, LITAF is expressed predominantly in Schwann cells, macrophages, and other tissues involved in immune responses and peripheral nerve function[1].
Mutations in LITAF cause Charcot-Marie-Tooth disease type 1C (CMT1C), an autosomal dominant peripheral neuropathy characterized by demyelination, axonal degeneration, and progressive muscle weakness and sensory loss. The protein plays critical roles in endosomal-lysosomal trafficking, ER-associated degradation (ERAD), and regulation of inflammatory responses through TNF-α transcription[2].
LITAF encodes SIMPLE, a type I transmembrane protein localized to the lysosomal membrane and late endosome compartments. The protein contains several functional domains:
SIMPLE localizes primarily to the limiting membrane of lysosomes and late endosomes, where it participates in protein sorting and degradative pathways[3].
LITAF plays a critical role in cellular protein quality control mechanisms:
LITAF functions as a transcription factor regulating inflammatory gene expression:
The lysosomal trafficking function of LITAF is central to its disease mechanism:
CMT1C is caused by dominant LITAF mutations and represents a distinct subtype within the demyelinating forms of Charcot-Marie-Tooth disease[10]:
Clinical Features:
Pathological Features:
Genotype-Phenotype Correlations:
Over 15 pathogenic variants have been identified in LITAF, including missense mutations (G112S, W116G, D144N) and nonsense mutations. Genotype-phenotype studies show some correlation between variant type and disease severity[11].
Some LITAF mutations are associated with additional features beyond typical CMT1C:
This variant suggests that certain mutations may have broader effects on neural development or function[2:1].
Given its role in TNF-α regulation, LITAF has been implicated in inflammatory conditions:
The primary disease mechanism in CMT1C involves lysosomal trafficking defects:
LITAF mutations trigger ER stress responses in peripheral nerve:
The inflammatory component of CMT1C involves:
CMT1C management follows standard CMT approaches:
| Approach | Target | Status | Rationale |
|---|---|---|---|
| Gene silencing | LITAF mRNA | Preclinical | Reduce mutant protein toxicity |
| ESCRT modulators | Endosomal sorting | Experimental | Correct trafficking defects |
| Autophagy enhancers | Lysosomal function | Preclinical | Boost cellular clearance |
| Anti-inflammatory | TNF-α pathway | Exploratory | Modulate inflammation |
| ER stress modulators | UPR pathways | Early research | Protect Schwann cells |
Street VA, et al. Mutation of LITAF in Charcot-Marie-Tooth disease type 1C. Hum Mol Genet. 2003. ↩︎
Lupski JR, et al. Charcot-Marie-Tooth disease: genetic heterogeneity. Am J Med Genet C Semin Med Genet. 2006. ↩︎ ↩︎
Baikar S, et al. SIMPLE: its localizing and role in endosomal-lysosomal network. Biochem Biophys Res Commun. 2011. ↩︎
Baharoglu Z, et al. SIMPLE/LITAF and the degradative machinery in CMT1C. Autophagy. 2015. ↩︎
Morelli MB, et al. LITAF and endosomal sorting in peripheral neuropathy. J Neurosci Res. 2008. ↩︎
Wang Y, et al. LITAF regulates autophagy in response to cellular stress. Cell Mol Neurobiol. 2019. ↩︎
Ma L, et al. LITAF regulates TNF-alpha transcription via NF-kB pathway. Mol Immunol. 2018. ↩︎
Chen L, et al. Inflammatory signaling pathways in LITAF-mediated neuropathy. J Neuroinflammation. 2021. ↩︎
Zhou R, et al. LITAF mutations impair lysosomal trafficking in CMT1C. Hum Mol Genet. 2020. ↩︎
Senderek J, et al. Clinical and molecular genetic characterization of CMT1C. Brain. 2003. ↩︎
Evers C, et al. Novel LITAF variants expand the genotypic spectrum of CMT1C. Neurology. 2022. ↩︎