Membrane Trafficking Lab

THE LAB

Welcome to our lab website!

Our Lab's primary research interest is to understand the regulation of copper transporters in mammalian cell. Copper Transporter 1, CTR1 is a channel which imports copper into the cell. ATP7A and ATP7B are the ATPases (pumps) which provide copper into the secretory pathway and also help to export excess copper out of the cells. Copper is an essential micro-nutrient, serves as co-factor in various metabolic pathways. But excess copper is toxic and detrimental to biological system as it heavily participates in redox reactions generating high amount of ROS. So, the amount of copper is tightly regulated inside a cell where CTR1 and ATP7A/B participates in maintaining intracellular copper homeostasis.

We mainly focus on the trafficking regulation of these copper transporters by using high resolution imaging technique along with molecular tools to address our questions. Beside these we also study the regulation of these transporters at molecular level using MD simulation. We are also trying to develop new imaging techniques and analysis programs.

Since our major focus is trafficking of copper transporters we call ourselves as 'TRAFFICKERS'.

We are also trying to tweak the copper metabolism pathway to combat platinum drug resistance in cancer. We collaborate with IISERK Chemistry group to develop better metal-based anticancer drugs. Additionally, we study the intricate changes in mammalian copper homeostasis pathway upon pathogen and its implication in disease fate.

Research topics

Regulation of copper importer protein CTR1

CTR1 is a high affinity copper importer channel that is present on the plasma membrane (review). It reduces environmetal Cu²⁺ to bioavailable Cu¹⁺ (J. Biol. Chem. 2022) as it imports copper to the cytoplasm where copper is distributed via chaperons (e.g. Atox1, CCS, COX17 etc.) present inside. This 35kDa protein trimerizes to form the functional channel pore. At high copper condition, CTR1 is endocytosed to restrict further copper entry inside cell. Apart from copper import, it is also been found to import anti-cancer drug Cisplatin inside cell. The exact mechanism of copper sensing, copper transport and endocytosis is till date unknown. In our lab, we are interested in... understanding these basics CTR1 regulation.

Regulation of homologous copper ATPase pump ATP7A and ATP7B

ATP7A and ATP7B are homologous P-type ATPase that share almost 60% sequence homology (review). They have six metal binding domains on the amino terminal that regulated their activity. At normal physiological condition, they reside on trans-Golgi network (TGN) and pump Atox1-acquired copper to the secretory pathway. At elevated copper condition, both ATP7A and ATP7B exit TGN and trafficks to baso-lateral and apical membrane respectively to export excess copper. This differential localisation accounts for systemic copper delivery by ATP7A in gut epithelia and excess copper excretion by ATP7B in liver. Mutations in ATP7A and ATP7B can result in Menken disease, Wilson Disease resulting in systemic copper deprivation and copper accumulation respectively In an unpolarised hepatocyte..., ATP7B trafficks to the lysosome and excess copper is excreted through lysosomal exocytosis (J. Cell. Sci. 2020). We have noticed copper independent trafficking of ATP7B too (Traffic 2023). Despite of high similarity, the basis of their differential trafficking is not well understood. Besides, due to their ligand mediated trafficking, they provide an exceptional model for studying polarised trafficking (J. Cell. Sci. 2023). In our lab, we are interested in understanding Trafficking regulation of ATP7A and ATP7B as a part of basic understanding of protein trafficking.

Role of copper in host-pathogen interaction using macrophage- Leishmania system

Despite the hostile microenvironment, Leishmania is known to thrive inside the phagosomes of macrophages. Copper, being a potent antimicrobial agent, has been effective against several intracellular pathogens. The study is aimed at revealing whether Leishmania faces copper stress during infection and if so, how do they evade such stress. The work has led to the discovery of a novel copper transporter, Cu ATPase in Leishmania that is crucial for its infectivity (J. Biol. Chem. 2022). The study also reveals an interplay between the macrophage copper ATPases (channelising copper to pathogen compartments) and the pathogenic counterpart neutralising the toxic effect by exporting the metal out. Presently, we are observing... an overall perturbation of cellular and systemic copper homeostasis pathway in host upon Leishmania infection, where we tried deciphering its causes and implications (pre-print).

Therapeutics for Wilson Disease and anti-cancer drugs

Wilson Disease is an autosomal recessive disorder that affects 1 in 30,000 people worldwide. It occurs due to a mutation in the ATP7B gene, leading to copper accumulation in the liver and, eventually, the brain. Currently, WD therapy includes using Cu-chelators (Penicillamine, Trientine, etc.) and Zinc salts to lower the copper load in the body. The significant drawbacks of available drugs are that they worsen neurological symptoms and cannot improve the downstream effects of copper accumulation, i.e., free radical generation, oxidative stress, and excessive autophagy. They cannot cross the blood-brain barrier, so the copper level in the brain does not deplete. In our lab..., we are trying to develop and check the potential of various small molecules that can chelate copper, reduce the downstream effect of copper accumulation, and cross the blood-brain barrier. We plan to develop a nanocarrier for hepato-specific delivery for Wilson disease, the main organ involved in this disease. Also, we works in collaboration for theraputics of anti-cancer drugs too (Inorg. Chem. 2019, Inorg. Chem. 2021, Biomatar. Sci. 2022).