Johnson, Christina K. et al. (2021) MicroPubl Biol

Miller, David D., Johnson, Christina K., Bianchi, Laura

[MicroPubl Biol, 2021]

MEC-4 and UNC-8 are subunits of the DEG/ENaC family of voltage-independent Na+ channels in C. elegans (Driscoll and Chalfie 1991, Canessa, Horisberger et al. 1993, Waldmann, Champigny et al. 1996, Waldmann, Champigny et al. 1997, de Weille, Bassilana et al. 1998, Waldmann and Lazdunski 1998). While MEC-4 is expressed in body touch neurons where it mediates the transduction of gentle touch sensation (Driscoll and Chalfie 1991, O'Hagan, Chalfie et al. 2005), UNC-8 is primarily expressed in motoneurons where it is involved in synaptic remodeling during development (Tavernarakis, Shreffler et al. 1997, Miller-Fleming, Petersen et al. 2016). Both MEC-4 and UNC-8 can be hyperactivated by genetic mutations that hinder channel closing, called (d) mutations (Driscoll and Chalfie 1991, Shreffler, Magardino et al. 1995, Goodman, Ernstrom et al. 2002, Wang, Matthewman et al. 2013). C. elegans neurons and Xenopus oocytes expressing these hyperactive variants of MEC-4 and UNC-8 undergo cell death due to uncontrolled flux of ions into the cell. Cell death in Xenopus oocytes and in cultured C. elegans neurons can be prevented by incubation with the DEG/ENaC channel blocker amiloride (Goodman, Ernstrom et al. 2002, Suzuki, Kerr et al. 2003, Wang, Matthewman et al. 2013).

Chen, Lili et al. (2020) MicroPubl Biol

Wang, Ya, Chen, Lili, Gao, Shangbang

[MicroPubl Biol, 2020]

The action potential (AP) is the basic signaling unit in various crucial physiological processing, for instance, in neurotransmission, muscle contraction, and glandular secretion (Koch, 1990). The classic model animal, Caenorhabditis elegans (or C. elegans), with a simple and compact nervous system, conservatively employs the calcium-mediated all-or-none APs for odor response in AWA olfactory neurons (Liu et al., 2018), as well as for muscle contraction in either body wall muscles (Gao and Zhen, 2011; Liu et al., 2011) and pharyngeal muscles (Davis et al., 1999). Plateau potentials were also observed in ASE and RMD neurons (Goodman et al., 1998; Mellem et al., 2008; Lockery et al., 2009; Lockery and Goodman, 2009), though the underlying roles in specific behavior are still elusive. Either in neurons or in muscles, the action potential firing is dependent on the excitatory pre-synaptic vesicles release. The minimum number of the presynaptic vesicles to elicit a single action potential in C. elegans has not been reported before. Here, by the combination of optogenetics with in-vivo patch clamping technology, we demonstrated that at least approximately 37 excitatory acetylcholinergic vesicles are required for the initiation of an action potential at post-synaptic body wall muscles.

Brown AL et al. (2007) J Gen Physiol "Gain-of-function mutations in the MEC-4 DEG/ENaC sensory mechanotransduction channel alter gating and drug blockade."

Brown AL, Goodman MB, Liao Z, Fernandez-Illescas SM

[J Gen Physiol, 2007]

MEC-4 and MEC-10 are the pore-forming subunits of the sensory mechanotransduction complex that mediates touch sensation in Caenorhabditis elegans (O''Hagan, R., M. Chalfie, and M.B. Goodman. 2005. Nat. Neurosci. 8:43-50). They are members of a large family of ion channel proteins, collectively termed DEG/ENaCs, which are expressed in epithelial cells and neurons. In Xenopus oocytes, MEC-4 can assemble into homomeric channels and coassemble with MEC-10 into heteromeric channels (Goodman, M.B., G.G. Ernstrom, D.S. Chelur, R. O''Hagan, C.A. Yao, and M. Chalfie. 2002. Nature. 415:1039-1042). To gain insight into the structure-function principles that govern gating and drug block, we analyzed the effect of gain-of-function mutations using a combination of two-electrode voltage clamp, single-channel recording, and outside-out macropatches. We found that mutation of A713, the d or degeneration position, to residues larger than cysteine increased macroscopic current, open probability, and open times in homomeric channels, suggesting that bulky residues at this position stabilize open states. Wild-type MEC-10 partially suppressed the effect of such mutations on macroscopic current, suggesting that subunit-subunit interactions regulate open probability. Additional support for this idea is derived from an analysis of macroscopic currents carried by single-mutant and double-mutant heteromeric channels. We also examined blockade by the diuretic amiloride and two related compounds. We found that mutation of A713 to threonine, glycine, or aspartate decreased the affinity of homomeric channels for amiloride. Unlike the increase in open probability, this effect was not related to size of the amino acid side chain, indicating that mutation at this site alters antagonist binding by an independent mechanism. Finally, we present evidence that amiloride block is diffusion limited in DEG/ENaC channels, suggesting that variations in amiloride affinity result from variations in binding energy as opposed to accessibility. We conclude that the d position is part of a key region in the channel functionally and structurally, possibly representing the beginning of a pore-forming domain.

Sela N et al. (2008) Biol Direct "Transduplication resulted in the incorporation of two protein-coding sequences into the turmoil-1 transposable element of C. elegans."

Ast G, Makalowski W, Sela N, Pupko T, Stern A

[Biol Direct, 2008]

ABSTRACT: Transposable elements may acquire unrelated gene fragments into their sequences in a process called transduplication. Transduplication of protein-coding genes is common in plants, but is unknown of in animals. Here, we report that the Turmoil-1 transposable element in C. elegans has incorporated two protein-coding sequences into its inverted terminal repeat (ITR) sequences. The ITRs of Turmoil-1 contain a conserved RNA recognition motif (RRM) that originated from the rsp-2 gene and a fragment from the protein-coding region of the cpg-3 gene. We further report that an open reading frame specific to C. elegans may have been created as a result of a Turmoil-1 insertion. Mutations at the 5'' splice site of this open reading frame may have reactivated the transduplicated RRM motif. Reviewers: This article was reviewed by Dan Graur and William Martin. For the full reviews, please go to the Reviewers'' Reports section.

Yu YB et al. (2010) PLoS One "Cinnamomum cassia bark in two herbal formulas increases life span in Caenorhabditis elegans via insulin signaling and stress response pathways."

Dosanjh L, Shim BS, Yu YB, Luo Y, Tan M, Lao L

[PLoS One, 2010]

BACKGROUND: Proving the efficacy and corresponding mode of action of herbal supplements is a difficult challenge for evidence-based herbal therapy. A major hurdle is the complexity of herbal preparations, many of which combine multiple herbs, particularly when the combination is assumed to be vitally important to the effectiveness of the herbal therapy. This issue may be addressed through the use of contemporary methodology and validated animal models. METHODS AND PRINCIPAL FINDINGS: In this study, two commonly used traditional herbal formulas, Shi Quan Da Bu Tang (SQDB) and Huo Luo Xiao Ling Dan (HLXL) were evaluated using a survival assay and oxidative stress biomarkers in a well-established C. elegans model of aging. HLXL is an eleven herb formula modified from a top-selling traditional herbal formula for the treatment of arthritic joint pain. SQDB consists of ten herbs often used for fatigue and energy, particularly in the aged. We demonstrate here that SQDB significantly extend life span in a C. elegans model of aging. Among all individual herbs tested, two herbs Cinnamomum cassia bark (Chinese pharmaceutical name: Cinnamomi Cortex, CIN) and Panax ginseng root (Chinese pharmaceutical name: Ginseng Radix, GS) significantly extended life span in C. elegans. CIN in both SQDB and HLXL formula extended life span via modulation of multiple longevity assurance genes, including genes involved in insulin signaling and stress response pathways. All the life-span-extending herbs (SQDB, CIN and GS) also attenuated levels of H2O2 and enhanced small heat shock protein expression. Furthermore, the life span-extending herbs significantly delayed human amyloid beta (Abeta)-induced toxicity in transgenic C. elegans expressing human Abeta. CONCLUSION/SIGNIFICANCE: These results validate an invertebrate model for rapid, systematic evaluation of commonly used Chinese herbal formulations and may provide insight for designing future evidence-based herbal therapy(s).