ERGIC2 (formerly known as
PTX1) is a gene identified by subtractive hybridization on the basis that it is expressed in normal human prostate, but not in prostate
carcinoma. It is unrelated to the gene encoding pituitary
homeobox protein (
Ptx1 or Pitx1), which regulates pituitary
hormone gene expression. Based on sequence homology with the yeast Erv41
protein, it is suggested that the ERGIC2
protein is an endoplasmic reticulum (ER) resident
protein involved in protein trafficking between the ER and Golgi intermediate compartment (ERGIC) and cis-Golgi. However, studies from our laboratory and others have shown that it may have other functions. In this study, we have identified a variant ERGIC2 transcript with a four base deletion at the junction of exons 8-9, resulting in frame shift after
codon #189. As a result, a truncated
protein of 215 residues (24.5 kDa) is predicted as compared with the 377-residue (42.6 kDa) wild-type (WT)
protein. The truncated variant ERGIC2
protein loses 45% of the
luminal domain and the transmembrane domain near the C-terminus, and this effectively abrogates its function as the ERGIC-Golgi protein transport shuttle. The variant, like the WT
protein, was found to upregulate the
heme oxygenase 1 gene, suggesting that it may be involved in the oxidative stress pathway.