Limiting transport steps and novel interactions of Connexin-43 along the secretory pathway

作者：Majoul Irina V^*; Onichtchouk Daria; Butkevich Eugenia; Wenzel Dirk; Chailakhyan Levon M; Duden Rainer

来源：Histochemistry and Cell Biology, 2009, 132(3): 263-280.

DOI：10.1007/s00418-009-0617-x

• Connexins
• Gap junction
• Arf
• COP
• FRET

Connexins are four-transmembrane-domain proteins expressed in all vertebrates which form permeable gap junction channels that connect cells. Here, we analysed Connexin-43 (Cx43) transport to the plasma membrane and studied the effects of small GTPases acting along the secretory pathway. We show that both GTP- and GDP-restricted Sar1 prevents exit of Cx43 from the endoplasmic reticulum (ER), but only GTP-restricted Sar1 arrests Cx43 in COP II-coated ER exit sites and accumulates 14-3-3 proteins in the ER fraction. FRET-FLIM data confirm that already in ER exit sites Cx43 exists in oligomeric form, suggesting an in vivo role for 14-3-3 in Cx43 oligomerization. Exit of Cx43 from the ER can be blocked by other factors-such as expression of the beta subunit of the COP I coat or p50/dynamitin that acts on the microtubule-based dynein motor complex. GTP-restricted Arf1 blocks Cx43 in the Golgi. Lastly, we show that GTP-restricted Arf6 removes Cx43 gap junction plaques from the cell-cell interface and targets them to degradation. These data provide a molecular explanation of how small GTPases act to regulate Cx43 transport through the secretory pathway, facilitating or abolishing cell-cell communication through gap junctions.

• 出版日期2009-9