AGR2

AGR2 Full Name

anterior gradient 2 homolog (Xenopus laevis)

AGR2 Introduction

Anterior Gradient 2 (AGR2) is a key secretory protein belonging to the anterior gradient family, which plays a crucial role in cell differentiation, tissue homeostasis, and protein folding. As a member of the protein disulfide isomerase (PDI) superfamily, AGR2 is predominantly expressed in secretory tissues, including the gastrointestinal tract, breast, lung, and reproductive organs, where it participates in the folding and maturation of secreted and transmembrane proteins. This protein contains a conserved thioredoxin-like domain that enables it to catalyze disulfide bond formation and isomerization, thereby ensuring the proper folding and function of target proteins. AGR2 is dynamically regulated during embryonic development and adult tissue repair, and its abnormal expression is closely linked to multiple physiological and pathological processes. Today, AGR2 is recognized not only as a critical regulator of protein homeostasis but also as a key biomarker and therapeutic target, with profound implications for oncology, developmental biology, and regenerative medicine.

Figure 1.The structure of AGR2 protein. (Zhang K, et al. 2023)

Expression Pattern and Regulatory Mechanisms of AGR2
AGR2 exhibits a tissue-specific and tightly regulated expression pattern, with prominent expression in secretory epithelia. In normal tissues, AGR2 is highly expressed in the stomach, intestine, breast, prostate, and lung, where it supports the secretion and maturation of functional proteins. Its expression is controlled by multiple regulatory mechanisms, including transcriptional regulation by transcription factors such as GATA6, HNF4α, and STAT3, as well as post-translational modifications (including phosphorylation and glycosylation) that modulate its secretion and enzymatic activity. In addition, AGR2 expression is dynamically altered in response to cellular stress, such as endoplasmic reticulum (ER) stress, where it participates in the unfolded protein response (UPR) to restore protein homeostasis. Aberrant regulation of AGR2, either through genetic or epigenetic modifications, leads to its overexpression or downregulation in various pathological conditions, particularly cancer.

Biological Functions of AGR2
AGR2 exerts diverse biological functions that are essential for normal physiology and pathological progression. Its primary function is to act as a protein disulfide isomerase, facilitating the folding and maturation of secreted and membrane-bound proteins, which is critical for maintaining the integrity and function of secretory tissues. Beyond protein folding, AGR2 plays a role in cell differentiation and tissue morphogenesis, particularly during embryonic development and tissue repair. It also modulates cellular processes such as cell proliferation, apoptosis, and epithelial-mesenchymal transition (EMT), which are key to normal tissue homeostasis and disease progression. Additionally, AGR2 has been shown to participate in immune regulation and inflammation, further expanding its biological significance.

Alternate Names for AGR2

AGR2; anterior gradient 2 homolog (Xenopus laevis); anterior gradient protein 2 homolog; AG2; HAG 2; PDIA17; protein disulfide isomerase family A; member 17; XAG 2; AG-2

• 1.Zhang K, et al. AGR2: a secreted protein worthy of attention in diagnosis and treatment of breast cancer. Frontiers in Oncology, 2023, 13: 1195885.