PNAS: a novel mechanism for potassium channel regulation

On January 6, 2023, the journal PNAS published a research paper entitled "DNA topoisomerase 2-associated proteins PATL1 and PATL2 regulate the biogenesis of hERG K+ channels" online, which was completed
by Cai Shiqing's research group of the Center for Excellence in Brain Science and Intelligent Technology (Institute of Neuroscience) of the Chinese Academy of Sciences 。 Taking advantage of the genetic advantages of Caenorhabditis elegans, the researchers identified the regulators of hERG channel production (Biogenesis) through forward genetic screening, and found that DNA topoisomerase 2-related proteins PATL1 and PATL2 regulate the transcription
of hERG channel genes.

Human ether-a-go-go related genes encode an inward rectified voltage-gated potassium channel (hERG), which is widely distributed and plays important physiological functions
in the heart and nervous system 。 The production process of hERG channels, including transcription, post-transcription, translation and post-translational modification, is precisely regulated, and if these regulatory mechanisms are deviated, too many or too few hERG channels on the cell membrane can lead to some serious human diseases, such as type 2 long QT syndrome, schizophrenia and cancer
.
Therefore, elucidating the molecular mechanisms of hERG channel biogenesis could provide new clues
to understanding the pathology of human diseases associated with hERG channel dysfunction.

The UNC-103 potassium channel of nematodes is highly homologous to the hERG channel, and is involved in regulating the movement and spawning behavior
of nematodes.
The researchers used UNC-103-expressing nematodes for forward genetic screening and found that the nematode DNA topoisomerase 2-related protein PATR-1 regulates the production of
UNC-103 channels.

Figure 1.
A, Screening strategy
for UNC-103 channel generation regulatory genes.
B, nematode DNA topoisomerase 2-related-protein PATR-1 regulates UNC-103 channel production
.
 

Subsequently, the researchers investigated whether human DNA topoisomerase 2-related proteins (PATL1 and PATL2) regulate the function of
hERG channels.
In human neuroblastoma cells and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), downregulation of PATL1 and PATL2 functions with small interfering RNAs significantly reduced the expression level and potassium current density of endogenous hERG channel proteins (Figures 2A and B).

Downregulation of PATL1 and PATL2 expression also prolonged the time course of action potentials of hiPSC-CMs, suggesting that PATL1 and PATL2 may affect the electrophysiological characteristics of cardiomyocytes (Figure 2C).

Analysis by the Diluciferase Reporter Gene Detection System found that PATL1 and PATL2 affect the synthesis of hERG mRNA (Figure 3).

Figure 2: Human DNA topoisomerase 2-related protein regulates hERG channel production
.
 

Figure 3: Human DNA topoisomerase 2-related proteins affect the transcription
of hERG channel mRNA.
 

It is generally believed that PATL1 and PATL2 are used as off-cap activators to promote mRNA degradation and as translation inhibitors to inhibit translation, and the study found that human DNA topoisomerase 2-related proteins PATL1 and PATL2 are new hERG channel formation regulators, regulating the transcription of hERG channel genes, revealing a new mechanism of regulating gene expression and broadening
。

The research work was mainly completed by postdoctoral researcher Yao Li under the guidance of researcher Cai Shiqing of the Center for Excellence of Brain Intelligence of the Chinese Academy of Sciences, and Ye Shiwei, a doctoral student at the Center for Excellence in Brain and Intelligence, Chinese Academy of Sciences, and Ruan Meiyu, a research assistant, made important contributions
to the project.
The research was strongly supported by the Molecular Cell Technology Platform and Optical Imaging Platform of the Center of Excellence for Brain Intelligence of the Chinese Academy of Sciences, and was funded
by the Ministry of Science and Technology, the Chinese Academy of Sciences, the National Natural Science Foundation of China and the Shanghai Municipality.