Visualization of Annular Gap Junction Vesicle Processing: The Interplay Between Annular Gap Junctions and Mitochondria.

It is becoming clear that in addition to gap junctions playing a role in cell⁻cell communication, gap junction proteins (connexins) located in cytoplasmic compartments may have other important functions. Mitochondrial connexin 43 (Cx43) is increased after ischemic preconditioning and has been suggested to play a protective role in the heart. How Cx43 traffics to the mitochondria and the interactions of mitochondria with other Cx43-containing structures are unclear.

Adrenocortical Gap Junctions and Their Functions.

Adrenal cortical steroidogenesis and proliferation are thought to be modulated by gap junction-mediated direct cell-cell communication of regulatory molecules between cells. Such communication is regulated by the number of gap junction channels between contacting cells, the rate at which information flows between these channels, and the rate of channel turnover. Knowledge of the factors regulating gap junction-mediated communication and the turnover process are critical to an understanding of adrenal cortical cell functions, including development, hormonal response to adrenocorticotropin, and neoplastic dedifferentiation.

Molecular mechanisms regulating formation, trafficking and processing of annular gap junctions.

Internalization of gap junction plaques results in the formation of annular gap junction vesicles. The factors that regulate the coordinated internalization of the gap junction plaques to form annular gap junction vesicles, and the subsequent events involved in annular gap junction processing have only relatively recently been investigated in detail. However it is becoming clear that while annular gap junction vesicles have been demonstrated to be degraded by autophagosomal and endo-lysosomal pathways, they undergo a number of additional processing events.

Redistribution of connexin 43 during cell division.

Gap junction channels, once clustered into gap junction plaques, allow communication of essential metabolites between cells. Gap junction plaques have been reported to be lost from the cell surface during cell division. The mechanism involved in this loss of gap junction plaques during mitosis is unclear, but we hypothesize that an endoexocytotic mechanism that results in cytoplasmic double-membraned annular gap junction vesicles is involved.