Localization and function of Pannexin2 isoform 202
Abstract
Pannexins (PANX) are a family of membrane glycoproteins comprised of 3 members: pannexin 1 (PANX1), pannexin 2 (PANX2), and pannexin 3 (PANX3). Oligomerized pannexin proteins form channels that allow for the passage of ions and small molecules. While PANX1 and PANX3 mostly localize to the cell surface, PANX2 remains intracellular within the endoplasmic reticulum (ER). Recently, a splice variant of PANX2 termed Panx2-202, was detected during development of murine skin. However, the localization and function of this shorter Panx2-202 isoform remains unknown. We found that Panx2-202 localizes to the ER in immortalized rat epidermal keratinocytes. We also found that expression of Panx2-202 in keratinocytes regulates mitochondria morphology. Collectively, we then hypothesized that Panx2-202 may regulate mitochondria morphology at the ER-mitochondria interface. We found that Panx2-202 colocalizes with split-GFP-based contact site sensor for the ER-mitochondria membrane. Lastly, Panx2 is a known substrate of caspase-3/7 cleavage at two residues in the C-terminal tail. These residues are present in Panx2-202, we presumed that the isoform also undergoes caspase-3/7 cleavage. Thus, we developed a novel tool to study C-terminal cleavage in living cells. Upon induction of apoptosis, the C-terminal tail of the Panx2-202 fused to a GFP tag containing a nuclear localization sequence was released from the ER membrane then trafficked to the nucleus. Overall, we defined the localization of Panx2-202 to the ER and identified a potential role in the regulation of mitochondria.