Ca²⁺-Affinitive and Non-Ca²⁺-Affinitive Synaptotagmins in Human Pan-cancer

Synaptotagmins (Syts) are a family of crucial Ca²⁺ sensors for cellular secretions, while half of the Syt isoforms are evolutionarily non-Ca²⁺-affinitive, which are less studied but associated with several neuro-system diseases. Some Syt isoforms exhibited importance in specific cancer types, but a comprehensive study of all Syts in pan-cancer is lacking. Here, using informatics tools and proteome/transcriptome databases, the expression, phosphorylation, CpG methylation profiles, and the correlation with genome heterogeneity, tumor stemness, and immune infiltration of all human Syts are analyzed in human pan-cancer, resulting in significant associations of each Syt in various types of cancer, including pathological stage and prognosis. Most Syts exhibit noteworthy expression level changes in GBM/LGG and PCPG, and Syt11 has a strong association with immune infiltration. The Ca²⁺-affinitive and non-Ca²⁺-affinitive Syt groups show opposite changes in both expression and methylation levels in an overview scale suggesting different mechanisms of them in cancers. Detection of similar expression genes suggests that Ca²⁺-affinitive Syts may participate in the RNA-splicing process, while non-Ca²⁺-affinitive Syts are involved in NF-κB signaling and immune regulation. This study uncovers the clinical potential of each Syt isoform and discusses clues to their roles, such as Ca²⁺ sensitivity and immune regulation, in tumor progression. The overall data are informative for future refining and mining.