Abstract
Connexins mediate intercellular communication by assembling into hexameric channel complexes that act as hemichannels and gap junction channels. Most connexins are characterized by a very rapid turn-over in a variety of cell systems. The regulation of connexin turn-over by phosphorylation and ubiquitination events has been well documented. Moreover, different pathways have been implicated in connexin degradation, including proteasomal and lysosomal-based pathways. Only recently, autophagy emerged as an important connexin-degradation pathway for different connexin isoforms. As such, conditions well known to induce autophagy have an immediate impact on the connexin-expression levels. This is not only limited to experimental conditions but also several pathophysiological conditions associated with autophagy (dys)function affect connexin levels and their presence at the cell surface as gap junctions. Finally, connexins are not only substrates of autophagy but also emerge as regulators of the autophagy process. In particular, several connexin isoforms appear to recruit pre-autophagosomal autophagy-related proteins, including Atg16 and PI3K-complex components, to the plasma membrane, thereby limiting their availability and capacity for regulating autophagy.
Highlights
A short overview of the autophagy process Autophagy is a term to describe the intracellular processes responsible for the delivery of the cell’s own macromolecules to the lysosomes for degradation and recycling [1]
Autophagy is emerging as an important connexin-degradation pathway under basal and normal growth conditions and wellestablished autophagy-inducing conditions like nutrient starvation and in a variety of pathological conditions
The degradation by autophagy is not limited to Cx43 but seems to contribute to the rapid turnover of many connexin isoforms, in particular during conditions of autophagy activation like nutrient starvation
Summary
A short overview of the autophagy process Autophagy (meaning “to eat oneself”) is a term to describe the intracellular processes responsible for the delivery of the cell’s own macromolecules to the lysosomes (or vacuoles) for degradation and recycling [1]. The degradation of Cx43 appeared to be mediated via the lysosomes but not the proteasome, since proteasomal inhibitors (MG132 or lactacystin) did not prevent the decline in Cx43-protein levels.
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