MEX3B (MEX3 RNA Binding Family Member B) is an RNA-binding protein that plays critical roles in post-transcriptional gene regulation, innate immune signaling, and RNA metabolism[@buchetpoyau2002]. Like other MEX3 family members, MEX3B contains KH domains that enable sequence-specific binding to RNA and regulate mRNA translation, stability, and subcellular localization[@dagostino2021].
MEX3B (MEX3 RNA Binding Family Member B) is an RNA-binding protein that plays critical roles in post-transcriptional gene regulation, innate immune signaling, and RNA metabolism[@buchetpoyau2002]. Like other MEX3 family members, MEX3B contains KH domains that enable sequence-specific binding to RNA and regulate mRNA translation, stability, and subcellular localization[@dagostino2021].
In the context of neurodegenerative diseases, MEX3B is of particular interest due to its involvement in RNA metabolism pathways disrupted in [amyotrophic lateral sclerosis (ALS)](/diseases/amyotrophic-lateral-sclerosis) and [frontotemporal dementia (FTD)](/diseases/frontotemporal-dementia)[@liuyesucevitz2020]. These disorders share common pathological features including TDP-43 proteinopathy, providing a mechanistic link between MEX3B dysfunction and disease pathogenesis.
Molecular Function
RNA Binding and Regulation
MEX3B encodes an RNA-binding protein with multiple cellular functions[@dagostino2021]:
Post-transcriptional regulation: Binds to specific mRNA sequences to regulate translation efficiency
mRNA stability: Modifies mRNA half-life through binding to 3' UTR regions
RNA granule localization: Participates in stress granules and processing bodies
Immune Signaling
MEX3B functions in innate immune pathways[@liu2022][@hiscott2005]:
The connection to TDP-43 pathology is particularly significant since TDP-43 inclusions are found in 95% of ALS cases and ~50% of FTD cases[@ratti2015][@highley2021].
Specific Mechanisms
RNA Toxicity
Aberrant RNA binding: MEX3B may bind to toxic RNA repeat expansions
Loss-of-function: Reduced activity leads to misregulation of essential neuronal transcripts
Gain-of-toxic-function: Altered protein may acquire novel toxic activities
Neuroinflammation
MEX3B modulates neuroinflammatory responses in the central nervous system[@heneka2019][@amoroso2022]:
Microglial activation: Regulates inflammatory gene expression in microglia