Decoding calcium oscillation frequency in transcriptional regulation

Abstract

Cells continuously experience fluctuating intracellular calcium (Ca{superscript 2}) signals that orchestrate diverse processes such as transcription, proliferation, and apoptosis. Temporal features of Ca{superscript 2} dynamics, including oscillation frequency, are hypothesized to encode information, allowing cells to discriminate between relevant and stochastic signals. However, the mechanisms of frequency decoding and their transcriptional consequences remain incompletely understood. To address this, we investigated how defined Ca{superscript 2} oscillation frequencies are translated into signaling cascades and gene expression programs in human non-excitable cells. Using optogenetic control of melanopsin-mediated Ca{superscript 2} influx, we induced slow (8 mHz) or fast (15 mHz) oscillations with identical single-pulse kinetics to isolate the effect of frequency. We found that TNF and IL8 transcription via NF-{kappa}B displayed sigmoidal frequency dependence, strictly requiring regular periodic stimulation, while random or low-frequency inputs with equal cumulative Ca{superscript 2} exposure were ineffective. Bulk RNA sequencing revealed a MYC-centered transcriptional response, with 116 of 215 differentially expressed genes predicted as MYC targets, despite unchanged MYC mRNA levels. Label-free phosphoproteomics identified PRKDC, CHEK2 and ATM as the top upstream kinases, forming a network linking Ca{superscript 2} oscillations to cell cycle and stress signaling. These findings demonstrate that cells can decode Ca{superscript 2} oscillation frequency through a multi-kinase network that tunes transcription via NF-{kappa}B and MYC, providing mechanistic insight into how temporal dynamics of second messengers shape cellular decision-making.