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Professor Surajit Ghosh

Surajit Ghosh and co-workers present a top-down approach to show how spatial positions of two tryptophans regulate the cellular entry and nuclear localization. Combining a wide range of physical-chemical and biological results, both in vitro and in part in vivo, this study provides fundamental insights on the positional importance of tryptophan and opens new opportunities for developing the next generation of cell-penetrating peptides and major-groove-specific anticancer drugs.

—Weihong Tan, Associate Editor, JACS

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Identification of key amino acids is required for development of efficient cell penetrating peptides (CPP) and has tremendous implications in medicine. Plasma membrane remains a tough barrier for smooth entry of drugs causing poor cellular uptake, requiring high amount of administered drugs to achieve the desired biological effect. Thus, efficient translocations of drugs through the plasma membrane are extremely important for its successful delivery and minimization of side effects on healthy tissues. This issue has been addressed in remarkable studies such as identification of Trans-Activator of Transcription (Tat) protein of the Human Immunodeficiency Virus (HIV) and Drosophila melanogaster Antennapedia homeodomain as important structural sequences for efficient translocation into the cells. Further studies reveal the minimum domain needed for translocation, which popularly termed as the CPPs. Extensive research work enlightened us about the importance of two amino acids, arginine and tryptophan in the cell penetration. Important point is to be noted that long CPP such as Tat causes amyloidogenecity in brain. Therefore, question remains, do we need long CPPs? To address this question, Dr. Surajit Ghosh’s group tried to understand the exact role of a tetrapeptide “Glu-Thr-Trp-Trp” (ETWW) derived from a long CPP “Pep1”. They presented a top-down approach to show how spatial positions of two tryptophans regulate the cellular entry and nuclear localization. This leads to the discovery of a short non-toxic tetrapeptides with excellent potential of cell penetration and nuclear localization. Through various experimental techniques, they showed that this CPP enters into the cancer cell following endocytic pathway and binds at major groove of nuclear DNA, where successive tryptophans plays major role. Subsequently, they showed that it is not a P-gp substrate and non-toxic to PC12 derived neurons, suggesting its excellent potential as CPP. Furthermore, its potential as CPP has been validated in stem cell like multi-cellular 3D cell culture (spheroid) and in in vivo mice model. This study provides major fundamental insights about the positional importance of tryptophan and opens new avenues towards development of next generation CPP and major groove specific anticancer drugs.

Reference:

Debmalya Bhunia, Prasenjit Mondal, Gaurav Das, Abhijit Saha, Pallabi Sengupta, Jagannath Jana, Saswat Mohapatra, Subhrangsu Chatterjee, and Surajit Ghosh.*
 
Spatial Position Regulates Power of Tryptophan: Discovery of Major Groove Specific Nuclear Localizing Cell Penetrating Tetrapeptide.
 
J Am Chem Soc., 2018, 140, 1697-1714.