Annexin II Light Chain p11 Interacts With ENaC to Increase Functional Activity at the Membrane

Abstract

The epithelial Na+ channel (ENaC) provides for Na+ absorption in various types of epithelia including the kidney, lung, and colon where ENaC is localized to the apical membrane to enable Na+ entry into the cell. The degree of Na+ entry via ENaC largely depends on the number of active channels localized to the cell membrane, and is tightly controlled by interactions with ubiquitin ligases, kinases, and G-proteins. While regulation of ENaC endocytosis has been well-studied, relatively little is understood of the proteins that govern ENaC exocytosis. We hypothesized that the annexin II light chain, p11, could participate in the transport of ENaC along the exocytic pathway. Our results demonstrate that all three ENaC channel subunits interacted with p11 in an in vitro binding assay. Furthermore, p11 was able to immunoprecipitate ENaC in epithelial cells. Quantitative mass spectrometry of affinity-purified ENaC-p11 complexes recovered several other trafficking proteins including HSP-90 and annexin A6. We also report that p11 exhibits a robust protein expression in cortical collecting duct epithelial cells. However, the expression of p11 in these cells was not influenced by either short-term or long-term exposure to aldosterone. To determine whether the p11 interaction affected ENaC function, we measured amiloride sensitive Na+ currents in Xenopus oocytes or mammalian epithelia co-expressing ENaC and p11 or a siRNA to p11. Results from these experiments showed that p11 significantly augmented ENaC current, whereas knockdown of p11 decreased current. Further, knockdown of p11 reduced ENaC cell surface population suggesting p11 promotes membrane insertion of ENaC. Overall, our findings reveal a novel protein interaction that controls the number of ENaC channels inserted at the membrane via the exocytic pathway.

An Epidemiological Survey Regarding Ticks and Tick-Borne Diseases among Livestock Owners in Punjab, Pakistan: A One Health Context

“…marginatum , and Hya. anatolicum were collected from humans (farmers and the general public) [ 69 ], highlighting the importance of better managing human-tick interactions in this region. The current study has reported several tick bites in home-based livestock settings, noting that most were simply ignored, which may represent an important public health concern for zoonotic transmission of TBDs.…”

Modulation of Ion Channels and Receptors by p11 (S100A10)

“…The roles for p11 in regulating ASIC1a functions in living animals remain to be delineated. p11 Increases Cell Surface Levels of Epithelial Na + Channel (ENaC) and Promotes Na + Absorption It has more recently been demonstrated that p11 binds ENaCs and regulates an exocytic pathway for these channels to the cell surface [35]. In vitro binding assay showed that p11 directly p11 retains TWIK-related acid sensitive K + channel-1 (TASK-1) channels in the endoplasmic reticulum, but increases cell surface levels of NaV1.8, acid-sensing ion channel-1 (ASIC-1), and epithelial Na + channel (ENaC).…”

Factors and Molecular Mechanisms Influencing the Protein Synthesis, Degradation and Membrane Trafficking of ASIC1a

“…Annexin II light chain p11, a member of the S100 family of small and dimeric EF-hand Ca 2+ -binding proteins, has been demonstrated to control the number of ENaCs present in the membrane via the exocytic pathway (Cheung et al, 2019). Considering that ASICs and ENaCs are both members of the DEG/ENaC gene family (Boscardin et al, 2016), it is rational to assume that p11 may have a regulatory effect on ASICs.…”