LITAF

LITAF Full Name

lipopolysaccharide-induced TNF factor

LITAF Introduction

LITAF, also known as SIMPLE (small integral membrane protein of the lysosome/late endosome), encodes a small, evolutionarily conserved protein that functions at the interface of innate immunity, endosomal trafficking, and gene transcription. Under resting conditions LITAF localizes largely to the cytoplasmic face of late endosomes and lysosomes, but in response to bacterial lipopolysaccharide (LPS) and other inflammatory cues it can translocate to the nucleus, where it acts as a transcription factor that drives expression of tumor necrosis factor alpha (TNF-α) and a constellation of other pro-inflammatory cytokines. Its ability to bind phosphoinositide lipids such as PI4P also places it within the machinery that controls vesicular traffic between the trans-Golgi network and recycling endosomes, linking membrane dynamics to immune signaling. This dual life, part organelle regulator and part transcriptional activator, explains why LITAF sits at a critical node in how cells perceive and respond to microbial threat.

Figure 1. Mechanisms of inflammation regulation by LITAF. (Source: Zou J, et al. 2015)

Genetic and functional studies have tied LITAF to a remarkably broad set of human conditions. In mouse models, deleting LITAF markedly blunts the surge of inflammatory cytokines after LPS challenge and protects animals from experimental endotoxic shock and inflammatory arthritis, while macrophage-specific loss reduces TNF-α secretion from the inflamed colon and dampens ulcerative-colitis-like injury. In cancer, LITAF is frequently downregulated and behaves like a tumor suppressor: restoring its expression suppresses proliferation and invasion in several tumor types, and reviews propose it as a switch balancing classical and alternative activation in the tumor microenvironment. On the other hand, missense mutations in LITAF cause Charcot-Marie-Tooth disease type 1C, a peripheral neuropathy in which the mutant protein mislocalizes from late endosomes and lysosomes to mitochondria, disrupting peripheral nerve maintenance. Together these observations position LITAF as a versatile sentinel whose proper localization and activity are essential for calibrated inflammation, tissue homeostasis, and disease resistance.

Alternate Names for LITAF

LITAF; lipopolysaccharide-induced TNF factor; lipopolysaccharide-induced tumor necrosis factor-alpha factor; FLJ38636; PIG7; SIMPLE; TP53I7; p53-induced gene 7 protein; LPS-induced TNF-alpha factor; tumor protein p53 inducible protein 7

• 1. Zou J, et al. Lipopolysaccharide-induced tumor necrosis factor-α factor enhances inflammation and is associated with cancer (Review). Mol Med Rep. 2015 Nov;12(5):6399-404.
  2. Bushell KN, et al. LITAF mediation of increased TNF-α secretion from inflamed colonic lamina propria macrophages. PLoS One. 2011;6(9):e25849.