The primary research interests of my lab focus on studying the molecular mechanisms regulating the trafficking towards late endosomes and lysosomes. Lysosomes are membrane-bound organelles present in eukaryotes which receive and degrade macromolecules from the endocytic, autophagic and phagocytic membrane trafficking pathways. Besides the normal degradative function, lysosomes are involved in mediating various physiological processes, including cholesterol homeostasis, plasma membrane repair, antigen presentation and microbial killing.
Recent studies have identified the role of small GTP-binding protein Arl8, a member of Arl (Arf-like) family of small GTPases in regulating lysosomal trafficking and phagosome-lysosome fusion. Arl8 is the first small GTP-binding protein shown to be localized primarily on lysosomal membranes. Upon GTP-binding, small GTPases like Arl8 recruit downstream tethering factors to intracellular membranes which permit vesicle docking and fusion with the target membranes. One such tethering complex recruited by Arl8 on lysosomal membranes is the HOPS (HOmotypic fusion and vacuole Protein Sorting)complex. We are characterizing the functions of different human HOPS complex subunits and the role of Arl8-HOPS interaction in regulating cargo trafficking towards lysosomes. To answer these questions we are using state-of-the-art techniques including confocal microscopy (both qualitative and quantitative imaging), flow cytometry-based assays, protein-protein interaction techniques including immunoprecipitations, GST-protein pulldown assays, purified protein-protein and protein-lipid interactions and yeast two-hybrid analysis.
Given that many diseases result from defects in the lysosomal trafficking pathway and the normal functioning of the lysosome is critical for immunity against wide variety of pathogens, our research will answer a key question of how lysosomal trafficking and function is regulated by Arl8 and its effectors.
- Devashish Dwivedi, Amrita Kumari, Siddhi Rathi, Sivaram V.S. Mylavarapu and Mahak Sharma*. The dynein adaptor Hook2 plays essential roles in mitotic progression and cytokinesis. *Corresponding author. Journal of Cell Biology, 218(3):871-894 (2019) [Featured on journal cover].
- Mahak Sharma* and Devashish Dwivedi. A CRACker of an adaptor connects dynein-mediated transport to calcium signaling. *Corresponding author. Journal of Cell Biology, 218(5):1429-1431 (2019) [Invited spotlight article].
- Amit Tuli* and Mahak Sharma*. How to do business with lysosomes: Salmonella leads the way. *Co-corresponding author. Current Opinion in Microbiology, 47:1-7 (2019) [Invited review].
- Aastha Sindhwani, Subhash B. Arya, Harmeet Kaur, Divya Jagga, Amit Tuli and Mahak Sharma*. Salmonella exploits the host endolysosomal tethering factor HOPS complex to promote its intravacuolar replication. *Corresponding author. PLOS Pathogens, 13(10):e1006700. DOI: 10.1371/journal.ppat.1006700 (2017).
- Rituraj Marwaha, Subhash B. Arya, Divya Jagga, Harmeet Kaur, Amit Tuli* and Mahak Sharma*. The Rab7 effector PLEKHM1 binds Arl8b to promote cargo traffic to lysosomes. *Co-corresponding author. Journal of Cell Biology, 216(4):1051-1070 (2017).
- Divya Khatter, Vivek B. Raina, Devashish Dwivedi, Aastha Sindhwani, Surbhi Bahl and Mahak Sharma*. The small GTPase Arl8b regulates assembly of the mammalian HOPS complex to lysosomes. *Corresponding author. Journal of Cell Science, 128(9):1746-1761 (2015).
- Divya Khatter, Aastha Sindhwani and Mahak Sharma*. Arf-like GTPase Arl8: Moving from the periphery to the center of lysosomal biology. *Corresponding author. Cellular Logistics, 5(3):e1086501 (2015) [Featured on journal cover]