Recombinant Human Dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit 2 (RPN2)

Introduction to Recombinant Human Dolichyl-diphosphooligosaccharide--protein Glycosyltransferase Subunit 2 (RPN2)

RPN2, also known as ribophorin II, is a subunit of the N-oligosaccharyltransferase (OST) complex, which is responsible for catalyzing the initial step in N-linked glycosylation, a crucial post-translational modification in eukaryotes . This modification involves the transfer of a pre-assembled glycan to specific asparagine residues on nascent polypeptide chains as they enter the endoplasmic reticulum (ER) .

Structure and Function

RPN2 is a type I transmembrane protein that plays a vital role in protein glycosylation and is essential for the proper folding, stability, and function of many glycoproteins . The protein contains multiple proteasome/cyclosome (PC) repeats that form a toroidal structure consisting of two concentric rings of $$\alpha$$ helices . The N-terminal domain, which is rod-like, and the C-terminal domain, which is globular, extend from one face of the toroid . The C-terminal domain binds to the ubiquitin receptor Rpn13 .

RPN2 in the 26S Proteasome

RPN2 is a subunit of the 19S regulatory particle (19S-RP) of the 26S proteasome, which is responsible for degrading ubiquitylated proteins . As a scaffolding subunit, RPN2, along with Rpn1, functions to engage ubiquitin receptors, facilitating the recognition, unfolding, and delivery of ubiquitylated substrates to the 20S core for proteolysis .

Clinical Significance

RPN2 has been implicated in various cancers, with its expression levels often correlating with disease progression and drug resistance . Studies have shown that RPN2 can regulate the glycosylation of multi-drug resistance proteins, such as P-glycoprotein, affecting the sensitivity of cancer cells to chemotherapeutic drugs .

• Non-Small Cell Lung Cancer (NSCLC): High RPN2 expression is correlated with early recurrence, distant metastasis, and poor survival in NSCLC patients . Silencing RPN2 can suppress cell proliferation and invasiveness and increase the sensitivity of lung cancer cells to chemotherapeutic drugs .

• Breast Cancer: RPN2 regulates tumor initiation and metastasis through the stabilization of mutant p53 . It also modulates docetaxel sensitivity in breast cancer cells through the glycosylation of P-glycoproteins .

• Esophageal Squamous Cell Carcinoma: RPN2 expression can predict the docetaxel response .

• Pancreatic Cancer: RPN2 is highly expressed in CD24+CD44+ cancer stem-like cells .

RPN2 as a Therapeutic Target

Given its involvement in cancer progression and drug resistance, RPN2 represents a potential therapeutic target. Targeting RPN2 through RNA interference (RNAi) has shown promise in preclinical studies, leading to cell death and increased sensitivity to chemotherapy in cancer cells .

Rpn13-Rpn2 Complex Structure

The C-terminal of Rpn2 interacts with Rpn13 . Specifically, the C-terminal 38 amino acids of hRpn2 are sufficient for interaction with hRpn13 . A study using isothermal titration calorimetry found that hRpn2 (940–953) binds to hRpn13 Pru with a dissociation constant (Kd) of 27±10 nM . Further truncation to hRpn2 (944–953) impaired binding, with an increased Kd value of 1.96±0.22 μM .

Interactions within the Rpn13-Rpn2 Complex

The Rpn13-Rpn2 complex involves extensive interactions, including proline-rich contacts. hRpn2 (940–953) includes four prolines, all of which interact with hRpn13 amino acids from a trans configuration . Strictly conserved P942, P944, and P945 bury hRpn13 W108 .

Steric Hindrance of RA190 Binding by Rpn2

The structure of the hRpn13-hRpn2 complex suggests that hRpn2 sterically blocks the RA190 binding site at C88 . RA190-conjugated hRpn13 Pru was not detected when the experiment was conducted with hRpn2 present, suggesting that RA190 cannot compete with hRpn2 (940–953) for hRpn13 Pru interaction .

Data Tables