The E3 ubiquitin ligase ITCH negatively regulates intercellular communication via gap junctions by targeting connexin43 for lysosomal degradation

Abstract

Cervix; Connexin; Endosome

Coll uterí; Connexina; endosoma

Cuello uterino; Conexina; Endosoma

Intercellular communication via gap junctions has a fundamental role in regulating cell growth and tissue homeostasis, and its dysregulation may be involved in cancer development and radio- and chemotherapy resistance. Connexin43 (Cx43) is the most ubiquitously expressed gap junction channel protein in human tissues. Emerging evidence indicates that dysregulation of the sorting of Cx43 to lysosomes is important in mediating the loss of Cx43-based gap junctions in cancer cells. However, the molecular basis underlying this process is currently poorly understood. Here, we identified the E3 ubiquitin ligase ITCH as a novel regulator of intercellular communication via gap junctions. We demonstrate that ITCH promotes loss of gap junctions in cervical cancer cells, which is associated with increased degradation of Cx43 in lysosomes. The data further indicate that ITCH interacts with and regulates Cx43 ubiquitination and that the ITCH-induced loss of Cx43-based gap junctions requires its catalytic HECT (homologous to E6-AP C-terminus) domain. The data also suggest that the ability of ITCH to efficiently promote loss of Cx43-based gap junctions and degradation of Cx43 depends on a functional PY (PPXY) motif in the C-terminal tail of Cx43. Together, these data provide new insights into the molecular basis underlying the degradation of Cx43 and have implications for the understanding of how intercellular communication via gap junctions is lost during cancer development.

Open access funding provided by University of Oslo (incl Oslo University Hospital). The study was supported by grants from the South-Eastern Norway Health Authority (grant number 2016013, E.L.); the Division for Cancer Medicine, Oslo University Hospital (grant number 2020-22, R.A.L.); the Kristian Gerhard Jebsen Foundation (the KGJ – Colorectal Cancer Research Centre, R.A.L.); and the Radium Hospital Legacy, Oslo (E.L.). T.A. acknowledges funding from Instituto de Salud Carlos III grant PI21/00470 co-financed by the European Regional Development Fund (ERDF), and Fundación Científica Asociación Española Contra el Cáncer (IDEAS SEMILLA AECC 2020/IDEAS20039AASE). Open access funding provided by University of Oslo (incl Oslo University Hospital).