Brsk2 Adaptive Changes In Energy Of The Pressure-induced Cell Cycle Regulation

Protein phosphorylation, an important regulatory component in signal transduction, plays a critical role in the regulation of many cellular functions and processes in eukaryotic as well as prokaryotic cells. The central components of phosphorylation, protein kinases achieve post-translational modification via the phosphorylation of serine, threonine and tyrosine residues, which controls many other cellular processes, including metabolism, transcription, cell cycle progression, cytoskeletal rearrangement and cell movement, apoptosis, and differentiation.BRSK2 is a serine/threonine protein kinase, belonging to the AMPK subfamily of CAMK family. Previous studies indicated that BRSK2 is expressed primarily in brain and is required for neuronal polarization and presynaptically regulates neurotransmitter release. While our study demonstrated that BRSK2 is expressed not only in brain but also highly in pancreas and these two tissues both correlate tightly with glucose. Moreover, as a member of AMPK subfamily, BRSK2 is likely regulated by energy stress. However, till now, nothing has been reported about the relationship between BRSK2 and energy stress. Our study on this point showed novel functions of BRSK2, especially in pancreas. We found that BRSK2 is activated by energy stress.On the other hand, we analyzed the protein sequence of BRSK2 and found a KOG0588 domain in 10-674 amino acid residues, which is related to control of cell cycle, cell division and chromosome separation. Thus we studied BRSK2's effect on cell cycle and the result showed that overexpressed BRSK2 arrested cell cycle in G2/M phase and increased accordingly the phosphorylation of CDC25C at Ser216 and Cdc2 at Tyr15, which are both checkpoint proteins. Our further study also demonstrated that BRSK2 can interact directly with CDC25C and phosphorylate it at Ser216, sequestering it to cytoplasm. And this might be the molecular mechanism of BRSK2 arresting cell cycle in G2/M phase.Aforementioned results made us further studied the correlation between energy stress and cell cycle and BRSK2's role in it. Although the correlation between energy stress and cell cycle is a fundamental problem in cell biology, there is still no certain conclusion on it, which might be caused by differences in the genetic background of the cells. Our study showed that cell cycle is arrested in G2/M phase when cellular energy is depleted in PANC-1 and the phosphorylation of CDC25C (Ser216) andCdc2 (Tyr15) correspondingly increases. Furthermore, transient transcription of PANC-1 cells with BRSK2-specific small interfering RNA duplexes significantly attenuated energy-stress-induced G2/M arrest, which suggested that BRSK2 functions as a key mediator in cell cycle regulation in response to cellular energy stress.In conclusion, we first proposed the key role of BRSK2 in regulating cell cycle in response to energy stress, which help us well learn the mechanism of cell cycle regulation.Lysophosphatidic acid acyltransferase (LPAAT) is an intrinsic membrane protein that catalyzes the synthesis of phosphatidic acid (PA) from lysophosphatidic acid (LPA). It is well known that LPAAT is involved in lipid biosynthesis, while its role in tumour progression has been of emerging interest in the last few years. To date, seven members of the LPAAT gene family have been found in human. Here we report a novel LPAAT member, designated as LPAAT-theta, which was 2728 base pairs in length and contained an open reading frame (ORF) encoding 434 amino acids. The LPAAT-theta gene consisted of 12 exons and 11 introns, and mapped to chromosome 4q21.23. LPAAT-theta was ubiquitously expressed in 18 human tissues by RT-PCR analysis. Subcellular localization of LPAAT-theta-EGFP fusion protein revealed that LPAAT-theta was distributed primarily in the endoplasmic reticulum (ER) of COS-7 cells. Furthermore, we found that the overexpression of LPAAT-theta can induce mTOR-dependent p70S6K phosphorylation on Thr389 and 4EBP1 phosphorylation on Ser65 in HEK293T cells.Moreover, we report here the cloning and characterization of a novel human cytoplasm-distribution zinc finger protein (CDZFP) gene, isolated from human ovary cDNA library, and mapped to 4pl2 by searching the UCSC genomic database. The CDZFP cDNA is 1793 base pairs in length and contains an open reading frame (ORF) encoding 236 amino acids. The CDZFP gene consists of 7 exons and encodes a putative zinc finger protein with a transmembrane region and two zinc finger motifs. Subcellular localization demonstrated that CDZFP protein was located in the cytoplasm when overexpressed in Hela cells and northern blot analysis revealed that CDZFP was ubiquitously expressed in 16 human tissues.