A biosensor to peer into the insides of a HIV infected cell

December 8, 2014

One of the unique features of the AIDS virus, HIV-1, is that it can exist inside human cells for years without causing any harm. It then reactivates to cause infection when conditions are suitable. Researchers from IISc, Bangalore, the International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi and Jamia Millia Islamia, New Delhi have exploited a non-invasive biosensor that can measure what is going on within HIV-1 infected cells in real-time.

This technology can offer insights which can help in controlling the AIDS infection and also provide insight on the interactions between HIV-1 and the tuberculosis causing bacteria, Mycobacterium tuberculosis (Mtb),within the cells.

Acquired Immune Deficiency Syndrome or AIDS is a devastating disease, which is unfortunately quite common. Since its discovery, AIDS has caused an estimated 36 million deaths worldwide (as of 2012). Its causative agent, the Human Immunodeficiency Virus (HIV), has thus been a hot topic of research.

Our body produces oxygen free radicals called Reactive Oxygen Species or ROS, during routine cellular metabolism. When not regulated properly, accumulation of these ROS can lead to oxidative stress. Heightened oxidative stress is one of the primary causes of reactivation of HIV-1 in infected cells.

Oxidative stress also decreases proliferation of disease fighting immune cells; besides, it causes loss of memory in immune cells. These factors reduce the efficiency of the immune response toward the HIV. A major cellular antioxidant called glutathione (GSH) functions as a protective shield against the oxidative stress. GSH levels in infected cells and tissues are indicators of the level of infection.

The team has devised a non-invasive biosensor methodology for precise measurements of GSH levels within HIV-1 infected cells. Earlier methods use whole cell or tissue extracts, which destroy detailed information related to the GSH levels in different areas within an infected cell. Study discovered that a modest increase in oxidative stress is sufficient to reactivate virus from latency. This may allow researchers to adopt a “shock-and-kill” strategy in which virus could be reactivated by oxidative stress inducing compounds and subsequently killed/flushed by current anti-HIV drugs. The fluctuation of GSH levels detected by the biosensor also helps understand the expression of antioxidant genes and related pathways during latent and active stages of infection.

The sensitivity and specificity of this biosensor could be further used in understanding the physiological changes in HIV-1 infected cells and the mechanism of drug action.

“Importantly, we also discovered that Mycobacterium tuberculosis, another major human pathogen, specifically disturbs glutathione balance to increase the replication of HIV. Since TB is the major cause of HIV related deaths, our findings have major mechanistic and therapeutic potential for both TB and AIDS (among the main causes of human death)”, said Dr. Singh.

The paper appeared in The Journal of Bilogical Chemistry on 18th November. DOI: 10.1074/jbc.M114.588913

An “antioxidant-like” protein to fight free radical damage in the body

September 22, 2014

A protein found in high levels in some cancer cells can be used for treating diseases caused by oxygen free radicals in the body, a recent study has found.

Oxygen free radicals such as hydrogen peroxides and superoxides, called Reactive Oxygen Species (ROS), are found in the cells as byproducts of cellular metabolism. Uncontrolled levels of ROS in the cell can lead to oxidative stress. Diabetes, atherosclerosis and neurodegenerative diseases like Parkinson’s and Alzheimer’s disease find their roots at the damage caused by oxidative stress in the cells.

Patrick D’Silva’s group at the Indian Institute of Science have found that Magmas, a mitochondrial protein also regulates the level of ROS in cells, apart from its already known function.

Magmas is involved in protein transport in cells, and is found in elevated levels in certain cancer types. There is very little information already available about regulation of ROS in the body, and this paper brings forth a lot of missing links in this research area.

The team found that the levels of Magmas in the cell are dependent on the cellular ROS levels. Elevated levels of Magmas help in lowering the concentration of ROS and vice versa. It not only plays an important role in controlling the production of free radicals, but maintains the ROS homeostasis by efficient scavenging. This protects the cell viability and also increases cellular stress tolerance.

“By maintaining a free-radical balance in cell, this protein prevents stress mediated cellular damage to biomolecules such as DNA, proteins and lipids. Hence, overproduction of Magmas protein provides unique advantages to the cells against free radical stress”, said Prof D’Silva.

Higher levels of Magmas are typically found in metabolically active tissues, cancer cells and tissues at different developmental stages. In cancer cells, Magmas prevents cell death, and hence helps in the proliferation of cancer cells. Even in non-cancerous cells, Magmas shows controlled levels of ROS and much lesser oxidative stress.

Such molecules that regulate the number of free radicals can be used while designing possible therapies for oxidative stress related disorders. “The inhibitors or stimulators against Magmas can be used as a therapeutic intervention against cancer as well as multiple free-radical induced stress related diseases”, said Prof D’Silva.

Further research is required to elucidate the mechanism of ROS regulation by Magmas and to discover the other proteins involved in the regulatory circuit.

The paper appeared in the journal Cell Death and Disease on 28th August 2014.

Link: http://www.nature.com/cddis/journal/v5/n8/full/cddis2014355a.html

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