Rhythms of Phosphatidylcholine Biosynthesis in Sinchronized Culture of Fibroblasts

*Corresponding author e-mail: vacosta@mail.fcq.unc.edu.ar Introduction: The circadian system that controls temporally physiology and behavior is composed of central pacemakers located in the brain and a network of peripheral oscillators distributed throughout the body. We have reported that the biosynthesis of phospholipids oscillates daily in synchronized fibroblast cultures under an intrinsic clock control involving the expression of the clock protein mPerl. However, it is unknown how the synthesis of phosphatidylcholine (PC), the most abundant eukaryotic cell lipid, is regulated along the day in cell cultures. The main pathway of PC synthesis in all mammalian nucleated cells is the CDP: choline pathway -via of Kennedywith CTP: phosphocholine cytidylyltranferase (CCT) as key enzyme. In mammals, there are two genes encoding for CCT: Pcyt1a that encodes the CCTß protein from alternative transcripts termed CCTß1 and CCTß2 and Pcyt1b gene that encodes the CCTß2 and CCTß3 proteins from differentially alternative spliced mRNA CCTß2 and CCTß3. CCTß is predominantly a nuclear protein in most cell types and is also found associated with the Endoplasmatic Reticulum (ER) and Golgi. In contrast, CCTß is excluded from the nucleus and is primarily localized to the ER compartment and Golgi complex. CCTß protein is ubiquitously expressed in nucleated cells and is tightly regulated at both transcriptional and post-transcriptional levels. However, CCTß proteins are most abundant in brain and gonads and little is known about the molecular mechanism involved in the transcriptional regulation of its gene. Results and conclusion: Here, we show that the synthesis of PC in synchronized cultures of NIH 3T3 cells exhibits a daily variation with higher levels at 6.5 h post serum shock. Similar changes were found in total CCT activity presenting higher levels at 6.5 h and 35 h post stimulation. We found detectable mRNA levels for all the CCT isoforms by RT-PCR in the cultures and a daily variation in some of those mRNA isoforms. Preliminary data show a daily variation in CCTß protein levels by Western Blot. The results suggest that the biosynthesis of PC in cultured fibroblast display a daily variation that is accompanied by similar changes in CCT enzyme activity as well as in mRNA and protein levels for the isoform ß. Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil