Cap1, short for Cyclase-Associated Protein 1, is a ubiquitously expressed protein that plays multiple essential roles. It is highly conserved in evolution and is involved in regulating actin dynamics [1,2,5,6]. Additionally, it participates in signaling pathways related to cAMP dynamics, such as the cAMP-Epac-PKA-Rap1 pathway which is relevant to cell adhesion [3,4]. CAP1 is crucial for various biological processes including cell proliferation, migration, and differentiation [1,2,6]. Genetic models, like knockout models, are valuable for studying its functions.

In Arabidopsis, knockout of Cap1 leads to defects in seed germination, seedling morphology, and seed production due to disrupted pollen tube elongation. However, the cap1-1 mutant shows increased tolerance to salt and mannitol treatment, indicating Cap1 plays a negative role in osmotic stress tolerance in plants [7]. In mouse cerebral cortex, inactivation of Cap1 reduces actin monomers in the cytoplasm, promoting nuclear MRTF translocation and MRTF-SRF activation, suggesting Cap1 represses MRTF-SRF-dependent gene expression [5]. In lung cancer, knockdown of Cap1 in A549 cells inhibits proliferation and migration, and phosphorylated sites S308 and S310 in Cap1 promote lung cancer cell proliferation, migration, and metastasis [1].

In conclusion, Cap1 is a multifunctional protein involved in actin dynamics, cAMP-related signaling, and various biological processes. Gene knockout models in different organisms, such as Arabidopsis and mice, have revealed its role in plant development, osmotic stress response, and mammalian gene regulation and cancer-related processes. Understanding Cap1's functions provides insights into disease mechanisms and potential therapeutic targets, especially in cancer research.