Effect of tetracycline family of antibiotics on actin aggregation, resulting in the formation of Hirano bodies responsible for neuropathological disorders

Abstract

Actin, an ATPase superfamily protein, regulates some vital biological functions like cell locomotion, cytokinesis, synaptic plasticity and cell signaling in higher eukaryotes, and is dependent on the dynamics of actin polymerization process. Impaired regulation of actin polymerization has been implicated in the formation and deposition of rod-like paracrystalline structures called as Hirano bodies in neuronal cells of patients suffering from Alzheimer’s disease, Pick’s disease, Guam amyotrophic lateral sclerosis and parkinsonism–dementia complex. Aggregation of actin forming amorphous deposition in the brain cells is also associated with chronic alcoholism and aging of the neurons. In the current article, we propose the breaking of the highly amorphous and dysregulated actin aggregates using generic compounds like tetracycline, oxytetracycline, doxycycline and minocycline which are used as antibiotics against tuberculosis and infection caused due to various Gram-negative bacteria. We have investigated the effect and affinity of binding of these four compounds to that of actin aggregates using 90° light scattering, size exclusion chromatography, dynamic light scattering, circular dichroism, scanning electron microscopy, transmission electron microscopy imaging and kinetic analysis. The isothermal calorimetric measurements showed that the binding constant for the cycline family molecules used in this study range from 9.8 E4 M⁻¹ to 1.3 E4 M⁻¹. To understand the in vivo effect, we also studied the effect of these drugs on Saccharomyces cerevisiae Δend3 mutant cells. Our data suggest that these generic compounds can plausibly be used for the treatment of various neurodegenerative diseases occurring due to Hirano body formation in brain cells.

Communicated by Ramaswamy H. Sarma

Keywords:

• Polymerization
• Hirano bodies
• aggregation
• protofilament
• Guam amyotrophic lateral sclerosis
• isothermal calorimetric assay

Acknowledgements

Authors would like to acknowledge Dr. Arvind Sahu for allowing them to carry out CD experiments at National Centre for Cell Sciences, Pune; Dr. Prabhakar Dongre for allowing them to carry out DLS measurements at Department of Biophysics, Mumbai University; Nanomaterials Laboratory for their state-of-art electron microscopy lab for SEM imaging; and Dr. Anand Ballal for his help with TEM imaging at Bhabha Atomic Research Centre, Mumbai.

Disclosure statement

Samridhi Pathak, Sarita Tripathi, Nayan Deori, Basir Ahmad, Hriday Verma, Rama Lokhande, Shirisha Nagotu, and Avinash Kale declare that they have no conflict of interest.

Compliance with ethics guidelines

This article does not contain any studies with human or animal subjects performed by the any of the authors. Necessary ethical clearance to work with Pig thigh muscle was obtained from Institutional Biosafety Committee of UM-DAE Centre for Excellence in Basic Sciences.

Additional information

Funding

Authors would like to acknowledges Department of Biotechnology (DBT), Ministry of Science and Technology, Government of India (Grant number: BT/PR16325/NER/95/117/2015) for partial financial support.