Abstract

BackgroundThe physiological processes in the cell are regulated by reversible, electrostatic protein-protein interactions. Apoptosis is such a regulated process, which is critically important in tissue homeostasis and development and leads to complete disintegration of the cell. Pathological apoptosis, a process similar to apoptosis, is associated with aging and infection. The current study shows that pathological apoptosis is a process caused by the covalent interactions between the signaling proteins, and a characteristic of this pathological network is the covalent binding of calmodulin to regulatory sequences.ResultsSmall molecules able to bind covalently to the amino group of lysine, histidine, arginine, or glutamine modify the regulatory sequences of the proteins. The present study analyzed the interaction of calmodulin with the BH3 sequence of Bax, and the calmodulin-binding sequence of myristoylated alanine-rich C-kinase substrate in the presence of xanthurenic acid in primary retinal epithelium cell cultures and murine epithelial fibroblast cell lines transformed with SV40 (wild type [WT], Bid knockout [Bid-/-], and Bax-/-/Bak-/- double knockout [DKO]). Cell death was observed to be associated with the covalent binding of calmodulin, in parallel, to the regulatory sequences of proteins. Xanthurenic acid is known to activate caspase-3 in primary cell cultures, and the results showed that this activation is also observed in WT and Bid-/- cells, but not in DKO cells. However, DKO cells were not protected against death, but high rates of cell death occurred by detachment.ConclusionsThe results showed that small molecules modify the basic amino acids in the regulatory sequences of proteins leading to covalent interactions between the modified sequences (e.g., calmodulin to calmodulin-binding sites). The formation of these polymers (aggregates) leads to an unregulated and, consequently, pathological protein network. The results suggest a mechanism for the involvement of small molecules in disease development. In the knockout cells, incorrect interactions between proteins were observed without the protein modification by small molecules, indicating the abnormality of the protein network in the transgenic system. The irreversible protein-protein interactions lead to protein aggregation and cell degeneration, which are observed in all aging-associated diseases.

Highlights

  • The physiological processes in the cell are regulated by reversible, electrostatic protein-protein interactions

  • The present study shows that the covalent modifications of proteins by xanthurenic acid lead to covalent, and subsequently nonregulated, interactions of calmodulin with the binding sites regulated by calmodulin and/ or phosphatidylinositol-4,5-phosphate, such as the effector domain (ED) sequence of myristoylated alanine-rich C-kinase substrate (MARCKS) and BH3 of Bax

  • We studied the mechanism of pathological apoptosis in the presence of xanthurenic acid in the retinal epithelial cells (RPE) primary cell culture and the cell culture of Murine embryonic fibroblast (MEF) cell lines transformed with SV40

Read more

Summary

Introduction

The physiological processes in the cell are regulated by reversible, electrostatic protein-protein interactions. Apoptosis is such a regulated process, which is critically important in tissue homeostasis and development and leads to complete disintegration of the cell. The current understanding suggests that too little apoptosis leads to. This understanding of apoptosis in disease development did not give a solution for the treatment of degenerative diseases and led to very toxic methods in cancer therapeutics. Many attempts have been made to heal aging-associated diseases by inhibiting the caspases The failure of this approach indicates that cell degeneration cannot be stopped by inhibition of the end-enzyme caspase. An upstream event is responsible for cell degenerative disorders

Methods
Results
Discussion
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call