RSU-1 Maintains Integrity of Caenorhabditis elegans Vulval Muscles by Regulating α-Actinin

RSU-1 regulates the integrity of dense bodies in muscle cells of aging Caenorhabditis elegans

Muscle contraction is vital for animal survival, and the sarcomere is the fundamental unit for this process. However, the functions of many conserved sarcomere proteins remain unknown, as their mutants do not exhibit obvious defects. To address this, Caenorhabditis elegans was utilized as a model organism to investigate RSU-1 function in the body wall muscle. RSU-1 is found to colocalize with UNC-97 at the dense body and M-line, and it is particularly crucial for regulating locomotion in aging worms, rather than in young worms. This suggests that RSU-1 has a specific function in maintaining muscle function during aging. Furthermore, the interaction between RSU-1 and UNC-97/PINCH is essential for RSU-1 to modulate locomotion, preserve filament structure, and sustain the M-line and dense body throughout aging. Overall, these findings highlight the significant contribution of RSU-1, through its interaction with UNC-97, in maintaining proper muscle cell function in aging worms.

Silencing of the T-type voltage-gated calcium channel α1 subunit by fungus-mediated RNAi altered the structure of F-actin and caused defective behaviors in Ditylenchus destructor

BACKGROUND

T-type calcium channels, characterized as low-voltage activated (LVA) calcium channels, play crucial physiological roles across a wide range of tissues, including both the neuronal and nonneuronal systems. Using in situ hybridization and RNA interference (RNAi) techniques in vitro, we previously identified the tissue distribution and physiological function of the T-type calcium channel α1 subunit (DdCα1G) in the plant-parasitic nematode Ditylenchus destructor.

METHODS AND RESULTS

To further characterize the functional role of DdCα1G, we employed a combination of immunohistochemistry and fungus-mediated RNAi and found that DdCα1G was clearly distributed in stylet-related tissue, oesophageal gland-related tissue, secretory-excretory duct-related tissue and male spicule-related tissue. Silencing DdCα1G led to impairments in the locomotion, feeding, reproductive ability and protein secretion of nematodes. To confirm the defects in behavior, we used phalloidin staining to examine muscle changes in DdCα1G-RNAi nematodes. Our observations demonstrated that defective behaviors are associated with related muscular atrophy.

CONCLUSION

Our findings provide a deeper understanding of the physiological functions of T-type calcium channels in plant-parasitic nematodes. The T-type calcium channel can be considered a promising target for sustainable nematode management practices.

Complex structures of Rsu1 and PINCH1 reveal a regulatory mechanism of the ILK/PINCH/Parvin complex for F-actin dynamics

Communications between actin filaments and integrin-mediated focal adhesion (FA) are crucial for cell adhesion and migration. As a core platform to organize FA proteins, the tripartite ILK/PINCH/Parvin (IPP) complex interacts with actin filaments to regulate the cytoskeleton-FA crosstalk. Rsu1, a Ras suppressor, is enriched in FA through PINCH1 and plays important roles in regulating F-actin structures. Here, we solved crystal structures of the Rsu1/PINCH1 complex, in which the leucine-rich-repeats of Rsu1 form a solenoid structure to tightly associate with the C-terminal region of PINCH1. Further structural analysis uncovered that the interaction between Rsu1 and PINCH1 blocks the IPP-mediated F-actin bundling by disrupting the binding of PINCH1 to actin. Consistently, overexpressing Rsu1 in HeLa cells impairs stress fiber formation and cell spreading. Together, our findings demonstrated that Rsu1 is critical for tuning the communication between F-actin and FA by interacting with the IPP complex and negatively modulating the F-actin bundling.