Effect of pH on the structure and function of cyclin-dependent kinase 6.

Mohd Yousuf,Abdelbaset Mohamed Elasbali,Farah Anjum,Md Imtaiyaz Hassan,Alaa Shafie,Qazi Mohd Rizwanul Haque,Asimul Islam,Dharmendra Kumar Yadav,Anas Shamsi,Shailza Singh

doi:10.1371/journal.pone.0263693

Mohd Yousuf, Abdelbaset Mohamed Elasbali + Show 8 more

Open Access

https://doi.org/10.1371/journal.pone.0263693

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Abstract

Cyclin-dependent kinase 6 (CDK6) is an important protein kinase that regulates cell growth, development, cell metabolism, inflammation, and apoptosis. Its overexpression is associated with reprogramming glucose metabolism through alternative pathways and apoptosis, which ultimately plays a significant role in cancer development. In the present study, we have investigated the structural and conformational changes in CDK6 at varying pH employing a multi-spectroscopic approach. Circular dichroism (CD) spectroscopy revealed at extremely acidic conditions (pH 2.0-4.0), the secondary structure of CDK6 got significantly disrupted, leading to aggregates formation. These aggregates were further characterized by employing Thioflavin T (ThT) fluorescence. No significant secondary structural changes were observed over the alkaline pH range (pH 7.0-11.0). Further, fluorescence and UV spectroscopy revealed that the tertiary structure of CDK6 was disrupted under extremely acidic conditions, with slight alteration occurring in mild acidic conditions. The tertiary structure remains intact over the entire alkaline range. Additionally, enzyme assay provided an insight into the functional aspect of CDK at varying pH; CDK6 activity was optimal in the pH range of 7.0-8.0. This study will provide a platform that provides newer insights into the pH-dependent dynamics and functional behavior of CDK6 in different CDK6 directed diseased conditions, viz. different types of cancers where changes in pH contribute to cancer development.

Highlights

Cyclin-Dependent Kinase 6 (CDK6) is an important regulatory protein of the cell cycle and metabolism [1]
CDK6 possesses 8 Tyr and 3 Trp residues, and we have investigated the effect of pH on the tertiary structure of CDK6 in terms of intrinsic fluorescence spectroscopy
CDK6 has a disrupted secondary structure when exposed to extreme acidic conditions, resulting in the formation of aggregates in this pH range, according to our findings

Summary

Introduction

Cyclin-Dependent Kinase 6 (CDK6) is an important regulatory protein of the cell cycle and metabolism [1]. It controls the G1-S phase transition of the cell cycle through the Rb-E2F pathway [2–5]. CDK6 is a key regulator in various cellular processes, such as cell proliferation [6– 8], differentiation [9–11], inflammation [12], apoptosis and cancer [1, 8, 13, 14], suggesting. Hassan Indian Council of Medical Research, 45/54/ 2018-PHA/BMS/OL, Mohd Yousuf The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

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