Autophagosome-lysosome fusion is facilitated by plectin-stabilized actin and keratin 8 during macroautophagic process

Autophagy is a lysosome-mediated degradative process that removes damaged proteins and organelles, during which autophagosome-lysosome fusion is a key step of the autophagic flux. Based on our observation that intermediate cytofilament keratin 8 (KRT8) enhances autophagic clearance in cells under oxidative stress condition, we investigated whether KRT8 supports the cytoplasmic architectural networks to facilitate the vesicular fusion entailing trafficking onto filamentous tracks. We found that KRT8 interacts with actin filaments via the cytolinker, plectin (PLEC) during trafficking of autophagosome. When PLEC was knocked down or KRT8 structure was collapsed by phosphorylation, autophagosome-lysosome fusion was attenuated. Inhibition of actin polymerization resulted in accumulation of autophagosomes owing to a decrease in autophagosome and lysosome fusion. Furthermore, myosin motor protein was found to be responsible for vesicular trafficking along the actin filaments to entail autolysosome formation. Thus, the autophagosome-lysosome fusion is aided by PLEC-stabilized actin filaments as well as intermediate cytofilament KRT8 that supports the structural integrity of actin filaments during macroautophagic process under oxidative stress condition.

Emerging insights into keratin 7 roles in tumor progression and metastasis of cancers

Keratin 7 (KRT7), also known as cytokeratin-7 (CK-7) or K7, constitutes the principal constituent of the intermediate filament cytoskeleton and is primarily expressed in the simple epithelia lining the cavities of the internal organs, glandular ducts, and blood vessels. Various pathological conditions, including cancer, have been linked to the abnormal expression of KRT7. KRT7 overexpression promotes tumor progression and metastasis in different human cancers, although the mechanisms of these processes caused by KRT7 have yet to be established. Studies have indicated that the suppression of KRT7 leads to rapid regression of tumors, highlighting the potential of KRT7 as a novel candidate for therapeutic interventions. This review aims to delineate the various roles played by KRT7 in the progression and metastasis of different human malignancies and to investigate its prognostic significance in cancer treatment. Finally, the differential diagnosis of cancers based on the KRT7 is emphasized.