ENaC proteolytic regulation by channel-activating protease 2
Agustín García-Caballero1, Yan Dang, Hong He
1Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, NC 27599, USA. acaballe@med.unc.edu
The Journal of General Physiology
|October 15, 2008
Summary
Channel-activating proteases (CAPs) activate epithelial sodium channels (ENaCs) through cleavage. This study identifies CAP2
Area of Science:
- Molecular biology
- Cell physiology
- Biochemistry
Background:
- Epithelial sodium channels (ENaCs) regulate Na(+) absorption, impacting blood pressure and airway function.
- Dysregulated ENaC activity is linked to hypertension and respiratory diseases.
- Proteolytic cleavage is a known mechanism for ENaC activation, with channel-activating proteases (CAPs) playing a key role.
Purpose of the Study:
- To investigate the specific cleavage sites of CAP2 (TMPRSS4) on ENaC subunits.
- To determine which CAP2-mediated cleavage events are responsible for ENaC activation.
- To elucidate the mechanism by which CAP2 regulates ENaC function.
Main Methods:
- Co-expression of ENaC subunits and CAP2 in oocytes.
- Site-directed mutagenesis of potential cleavage sites on ENaC subunits.
- Measurement of Na(+) currents (I(Na)) and analysis of ENaC fragments using electrophysiology and Western blotting.
Main Results:
- CAP2 cleaves all three ENaC subunits at multiple sites, including conserved basic residues.
- Cleavage at gamma-ENaC R138, a furin-consensus site, is essential for CAP2-induced ENaC activation and cell surface fragment generation.
- Mutating gamma-ENaC R138 to alanine or glutamine abolished CAP2-mediated Na(+) current and fragment formation, while mutation to lysine preserved these effects.
Conclusions:
- CAP2 activates ENaCs primarily through cleavage at the R138 site in the gamma-ENaC subunit.
- This specific cleavage event is critical for generating functional ENaC channel complexes at the cell surface.
- Understanding this mechanism provides insights into ENaC regulation and potential therapeutic targets for ENaC-related disorders.
Related Concept Videos
02:58Regulated Protein Degradation
It is vital to regulate the activity of enzymatic as well as non-enzymatic proteins inside the cell. This can be achieved either through creating a balance between their rate of synthesis and degradation or regulating the intrinsic activity of the protein. Both these regulation mechanisms play an essential role in the normal functioning of cells.
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
02:58Regulated Protein Degradation
It is vital to regulate the activity of enzymatic as well as non-enzymatic proteins inside the cell. This can be achieved either through creating a balance between their rate of synthesis and degradation or regulating the intrinsic activity of the protein. Both these regulation mechanisms play an essential role in the normal functioning of cells.
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
01:16Calmodulin-dependent Signaling
Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
01:45Regulation of Nuclear Protein Sorting
Nuclear protein sorting regulates nucleus composition and gene expression, crucial for determining the fate of a eukaryotic cell. Hence, the entry and exit of molecules across the nuclear envelope is a tightly controlled process. Nuclear protein sorting can be inhibited by one of the following ways: 1) masking cargo signal sequences, 2) modifying the nuclear receptor's affinity for cargo, 3) controlling the nuclear pore size, 4) retaining the cargo during its transit to the cytosol or the...
01:37The Unfolded Protein Response
The ER is the hub of protein synthesis in a cell. It has robust systems to quality control protein folding and also for degradation of terminally misfolded proteins. Under normal conditions, a small proportion of misfolded proteins that cannot be salvaged need to be transported to the cytoplasm by the ER-associated degradation or ERAD pathways. However, if the ERAD cannot handle the misfolded proteins, the cell activates the unfolded protein response or UPR to adjust the protein folding...
02:18The Proteasome
Eukaryotic cells can degrade proteins through several pathways. One of the most important amongst these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...