Targeting HPV-16 antigens to the endoplasmic reticulum induces an endoplasmic reticulum stress response

• Published in: Cell stress & chaperones Vol. 24; no. 1; pp. 149 - 158
• Main Authors: Martínez-Puente, David H., Pérez-Trujillo, José J., Gutiérrez-Puente, Yolanda, Rodríguez-Rocha, Humberto, García-García, Aracely, Saucedo-Cárdenas, Odila, Montes-de-Oca-Luna, Roberto, Loera-Arias, María J.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.01.2019; Springer Netherlands; Springer Nature B.V
• Subjects: Antigens; Antigens, Viral - metabolism; Autophagy; Biochemistry; Biomarkers - metabolism; Biomedical and Life Sciences; Biomedicine; Cancer; Cancer Research; Cancer vaccines; Cell Biology; Cycloheximide; Degradation; Deoxyribonucleic acid; DNA; DNA vaccines; Drug delivery systems; Endoplasmic reticulum; Endoplasmic Reticulum - metabolism; Endoplasmic Reticulum Chaperone BiP; Endoplasmic Reticulum Stress; HEK293 Cells; Human papillomavirus; Human papillomavirus 16 - metabolism; Humans; Immunology; Molecular Chaperones - metabolism; Mutants; Neurosciences; Original Paper; Phagocytosis; Proteasome Endopeptidase Complex - metabolism; Proteasomes; Protein biosynthesis; Protein synthesis; Proteins; Retention; Stress; Stress response; Ubiquitin - metabolism; Vaccines; Signal peptide; E7; KDEL signal; ER targeting; GRP78/BiP; Stress response
• ISSN: 1355-8145; 1466-1268
• DOI: 10.1007/s12192-018-0952-8

Very promising results have been observed with a deoxyribonucleic acid (DNA) vaccine based on human papillomavirus type-16 (HPV-16) antigen retention and delivery system in the endoplasmic reticulum (ER). However, the mechanism by which these antigens are processed once they reach this organelle is still unknown. Therefore, we evaluated whether this system awakens a stress response in the ER. Different DNA constructs based on E6 and E7 mutant antigens fused to an ER signal peptide (SP), a signal for retention in the ER (KDEL), or both signals (SPK), were transfected into HEK-293 cells. Overexpression of E6 and E7 antigens targeted to the ER (SP, and SPK constructs) induced ER stress, which was indicated by an increase of the ER-stressmarkers GRP78/BiP and CHOP. Additionally, the ER stress response was mediated by the ATF4 transcription factor, which was translocated into the nucleus. Besides, the overexpressed antigens were degraded by the proteasome. Through a cycloheximidechase assay, we demonstrated that when both protein synthesis and proteasome were inhibited, the overexpressed antigens were degraded. Interestingly, when proteasome was blocked autophagy was increased and the ER stress response decreased. Taken together, these results indicate that the antigens are initially degraded by the ERAD pathway, and autophagy degradation pathway can be induced to compensate the proteasome inhibition. Therefore, we provided a new insight into the mechanism by which E6 and E7 mutant antigens are processed once they reach the ER, which will help to improve the development of more effective vaccines against cancer.