Prolyl 4-hydroxylase subunit beta (P4HB), also known as protein disulfide isomerase A1 (PDIA1), is a multifunctional enzyme primarily localized in the endoplasmic reticulum (ER). It belongs to the protein disulfide isomerase family and plays a crucial role in catalyzing the formation, rearrangement, and breakage of disulfide bonds during protein folding.



Functionally, P4HB acts as a central regulator in protein disulfide isomerase activity and endoplasmic reticulum stress response pathways. It not only assists in proper protein folding but also functions as a molecular chaperone, preventing aggregation of misfolded proteins and maintaining ER homeostasis. In addition, as the beta subunit of prolyl 4-hydroxylase, P4HB is involved in collagen biosynthesis and extracellular matrix (ECM) remodeling, linking intracellular protein processing with tissue structure regulation.



In cancer research, P4HB has emerged as an important candidate amongP4HB biomarkers in cancer progression and ER stress-mediated tumor biology. Overexpression of P4HB has been reported in multiple tumor types, where it contributes to tumor growth, metastasis, and therapeutic resistance. Mechanistically, P4HB supports cancer cell survival by enhancing tolerance to ER stress, promoting angiogenesis, and facilitating extracellular matrix remodeling. Furthermore, recent studies suggest that P4HB may drive tumor invasion and metastasis through collagen maturation and redox signaling pathways.