The single-PDZ domain protein TXBP-3 regulates contractility in the C. elegans spermatheca
- 1Northeastern University
Abstract
In the C. elegans reproductive system, oocyte transit through the spermatheca relies on parallel calcium and Rho-dependent signaling pathways to regulate actomyosin contractility. Here, we identify the conserved single-PDZ domain protein TXBP-3/TAX1BP3 as a dosage-dependent regulator of spermathecal contractility. TXBP-3 is expressed in contractile tissues, including the spermatheca and spermathecal-uterine (sp-ut) valve. Animals lacking txbp-3 do not display overt phenotypes or defects in ovulation. However, in nematodes expressing the genetically encoded calcium sensor GCaMP, deletion of txbp-3 results in more rapid transit of embryos through the spermatheca. Conversely, tissue-specific overexpression of TXBP-3 results in slower transit times due to hypercontraction of the spermathecal neck and sp-ut valve, causing oocyte severing and failures of embryos to exit the spermatheca. We find TXBP-3 promotes the active phosphorylated state of the calcium/calmodulin-dependent protein kinase II (CaMKII) UNC-43. When TXBP-3 is overexpressed or unc-43 is depleted, ovulations in which the embryo fails to exit show disrupted calcium signaling. Additionally, TXBP-3 functions independently of the RhoGEF RHGF-1 and in parallel with the RhoGAP SPV-1 to maintain the alignment of actin fiber bundles and protect embryo structural integrity. Together, our results establish TXBP-3 as a regulator of contractility, kinase activation, and cytoskeletal architecture in contractile tissues.
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BibTeX
@misc{khalid2026singlepdz,
title = {{The single-PDZ domain protein TXBP-3 regulates contractility in the C. elegans spermatheca}},
author = {M. Khalid and E. J. Cram},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.05.756805},
url = {https://www.biorxiv.org/content/10.64898/2026.10.05.756805v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - The single-PDZ domain protein TXBP-3 regulates contractility in the C. elegans spermatheca
AU - M. Khalid
AU - E. J. Cram
PY - 2026
DA - 2026/10/05
PB - bioRxiv
DO - 10.64898/2026.10.05.756805
UR - https://www.biorxiv.org/content/10.64898/2026.10.05.756805v1
AB - In the C. elegans reproductive system, oocyte transit through the spermatheca relies on parallel calcium and Rho-dependent signaling pathways to regulate actomyosin contractility. Here, we identify the conserved single-PDZ domain protein TXBP-3/TAX1BP3 as a dosage-dependent regulator of spermathecal contractility. TXBP-3 is expressed in contractile tissues, including the spermatheca and spermathecal-uterine (sp-ut) valve. Animals lacking txbp-3 do not display overt phenotypes or defects in ovulation. However, in nematodes expressing the genetically encoded calcium sensor GCaMP, deletion of txbp-3 results in more rapid transit of embryos through the spermatheca. Conversely, tissue-specific overexpression of TXBP-3 results in slower transit times due to hypercontraction of the spermathecal neck and sp-ut valve, causing oocyte severing and failures of embryos to exit the spermatheca. We find TXBP-3 promotes the active phosphorylated state of the calcium/calmodulin-dependent protein kinase II (CaMKII) UNC-43. When TXBP-3 is overexpressed or unc-43 is depleted, ovulations in which the embryo fails to exit show disrupted calcium signaling. Additionally, TXBP-3 functions independently of the RhoGEF RHGF-1 and in parallel with the RhoGAP SPV-1 to maintain the alignment of actin fiber bundles and protect embryo structural integrity. Together, our results establish TXBP-3 as a regulator of contractility, kinase activation, and cytoskeletal architecture in contractile tissues.
ER -