Internal translation of the connexin 43 transcript

Area of Science:

• Molecular biology
• Cellular biology
• Biochemistry

Background:

• Connexin 43 (Cx43) is a key gap junction protein involved in numerous physiological and pathological processes.
• Cx43 functions can be independent of gap junctions, relying on C-terminal fragments.
• Naturally occurring Cx43 C-terminal isoforms are generated through internal translation.

Purpose of the Study:

• To confirm and characterize the internal translation of Cx43 C-terminal domains.
• To elucidate the regulatory mechanisms governing Cx43 internal translation.
• To investigate the signaling pathways involved in the generation of Cx43 isoforms.

Main Methods:

• Direct RNA transfection experiments were performed.
• Inhibitors and knockout mouse cells were utilized to study signaling pathways.
• Ribosomal scanning and upstream translation requirements were assessed.

Main Results:

• Internal translation of Cx43 C-terminal domains, particularly the 20-kDa isoform, was confirmed from a single GJA1 gene transcript.
• Internal translation requires upstream translation and is not a cap-independent IRES-mediated mechanism.
• The Mnk1/2 pathway, in addition to the mTOR pathway, was identified as a regulator of the 20-kDa Cx43 isoform.

Conclusions:

• Cx43 transcript internal translation is confirmed, requiring upstream translation.
• The PI3K/AKT/mTOR and Mnk1/2 pathways regulate the major 20-kDa Cx43 isoform.
• Findings have significant implications for understanding Cx43's role in cancer and other diseases, highlighting internal mRNA translation as a source of protein diversity.