Isoform 5 of Rho guanine nucleotide exchange factor 18

# ARHGEF18 Isoform 5 Summary

ARHGEF18 encodes a Rho guanine nucleotide exchange factor, a molecular class that regulates actin cytoskeleton dynamics and cell morphology through activation of Rho family GTPases (UniProt: Q6ZSZ5-1). The protein is a guanine nucleotide exchange factor (GEF) that catalyzes nucleotide exchange on Rho-family proteins, thereby controlling their activation state and downstream signaling. Isoform 5 is a 1173 amino acid variant with a molecular mass of approximately 131 kDa.

ARHGEF18 is expressed in the brain where Rho signaling influences neuronal morphogenesis, synaptic plasticity, and axonal guidance. The protein's role in regulating the actin cytoskeleton implicates it in processes fundamental to neuronal structure and function. No specific tissue tropism or pathway annotations are available in the current record.

In Alzheimer's disease, ARHGEF18 isoform 5 is significantly downregulated in post-mortem AD brain tissue relative to age-matched controls (Chaparral AD proteomics). The mean log2 fold-change is −0.2464 across examined subcellular fractions in TMT-labeled proteomics data. This downregulation may reflect loss of cytoskeletal regulation capacity and altered neuronal morphological dynamics in AD pathology.