Thermal nociception in Caenorhabditis elegans is regulated by the Ca²⁺/calmodulin-dependent protein kinase CMK-1, but its downstream effectors have remained unclear. Here, we combined in vitro kinase assays with mass-spectrometry-based phosphoproteomics to identify hundreds of CMK-1 substrates, including the calcineurin A subunit TAX-6, phosphorylated within its conserved regulatory domain. Genetic and pharmacological analyses reveal multiple antagonistic interactions between CMK-1 and calcineurin signaling in modulating both naive thermal responsiveness and adaptation to repeated noxious stimuli. Cell-specific manipulations indicate that CMK-1 acts in AFD and ASER thermo-sensory neurons, while TAX-6 functions in FLP thermo-sensory neurons and downstream interneurons. Since CMK-1 and TAX-6 act in distinct cell types, the phosphorylation observed in vitro might not directly underlie the behavioral phenotype. Instead, the opposing effects seem to arise from their distributed roles within the sensory circuit. Overall, our study provides (1) a resource of candidate CMK-1 targets for further dissecting CaM kinase signaling and (2) evidence of a previously unrecognized, circuit-level antagonism between CMK-1 and calcineurin pathways. These findings highlight a complex interplay of signaling modules that modulate thermal nociception and adaptation, offering new insights into potentially conserved mechanisms that shape nociceptive plasticity and pain (de)sensitization in more complex nervous systems.

The six-subunit ORC is essential for the initiation of DNA replication in eukaryotes. Cancer cell lines in culture can survive and replicate DNA replication after genetic inactivation of individual ORC subunits, ORC1, ORC2, or ORC5. In primary cells, ORC1 was dispensable in the mouse liver for endo-reduplication, but this could be explained by the ORC1 homolog, CDC6, substituting for ORC1 to restore functional ORC. Here, we have created mice with a conditional deletion of ORC2, which does not have a homolog. Although mouse embryo fibroblasts require ORC2 for proliferation, mouse hepatocytes synthesize DNA in cell culture and endo-reduplicate in vivo without ORC2. Mouse livers endo-reduplicate after simultaneous deletion of ORC1 and ORC2 both during normal development and after partial hepatectomy. Since endo-reduplication initiates DNA synthesis like normal S phase replication these results unequivocally indicate that primary cells, like cancer cell lines, can load MCM2-7 and initiate replication without ORC.