Office Phone: +91-22-27405109
Laboratory Phone: +91-22-2740 5330
Fax: +91-22-2740 5085
One Key Research Area: Apoptosis
Special interests:Apoptosis, Biophysics, Structural Biology, Enzymology
About us: The focus of the laboratory is to understand the underlying mechanism of alternative non-classical pathways of programmed cell death (apoptosis). Apoptosis is a fundamental cellular process essential to maintain a healthy life. Disruption of the fine balance between cell survival and death leads to several life-threatening diseases such as neurodegenerative disorders and cancer. Cancer is characterized by a breakdown in the cellular apoptotic machinery, which might be due to alteration of structural and functional properties of critical proteins in the apoptotic pathway. Interaction between pro- and anti-apoptotic proteins is closely related to the genesis and progression of cancer. Therefore, identifying the binding partners of pro-apoptotic proteins and understanding the determinants of such interactions will not only help delineate their biological roles but will also help design their peptide and non-peptide mimetics that would disrupt the interactions, promote apoptosis and hence regulate tumorigenesis.
1. Understanding protein-protein interactions involved in papillomavirus E2 induced apoptosis
Early protein E2 of high-risk human papillomaviruses (HPV-16 and -18) that carry out essential viral functions are also found to be proapoptotic. Although the exact mechanism is unclear, recent literature suggests that in HPV-18 E2, the N-terminal transactivation domain directly interacts with procaspase-8, a component of Death Inducing Signaling Complex (DISC) in the extrinsic cell death pathway. This interaction bypasses the requirement of upstream adaptor proteins which are essentially required for DISC formation, thereby representing a novel adaptor-independent caspase activation pathway. In this work, we are studying this unique interaction using an interdisciplinary approach employing techniques such as insilico, mutational, biochemical and biophysical analyses. Our results would provide a molecular basis of this novel E2-procaspase-8 interaction and help in providing a model for E2-induced apoptosis in high risk HPV types.
2. Proapoptotic serine protease HtrA2/Omi: structural determinants of its mechanism of action
HtrA2 is a mitochondrial proapoptotic serine protease that is capable of inducing apoptosis both in capase-dependent as well as independent manner via its serine protease activity. However, the mechanism of HtrA2 mediated proteolysis and hence apoptosis is poorly understood due to the limited number of identified substrates as well as its structural complexity. Although PDZ (C-terminal domain) is the well-known interaction domain for HtrA2 substrates, recent literature suggests IAPs do bind the N-terminal of HtrA2 resulting in its activation followed by IAP cleavage. Thus, the role of PDZ and other domains in mediating HtrA2 functions is being studied in our laboratory using biochemical, biophysical and cell biology tools with an aim at developing a unified model for substrate-binding and cleavage by HtrA2.
3. Role of HtrA2 in Regulating Its Specificity and Functions
HtrA2/Omi is a unique trimeric serine protease that performs several critical cellular functions in a coordinated fashion, the mechanism of which still remains elusive. Although, HtrA2 has primarily been identified as an IAP (Inhibitor of Apoptosis) binding proapoptotic protein, its caspase-independent apoptotic function and serine protease activity are poorly characterized. Recent studies have identified a cytoplasmic antiapoptotic substrate of HtrA2 (Ped/Pea-15) suggesting its proapoptotic and proteolytic functions might converge. Moreover, high sequence similarity with its E. coli counterpart HtrA, as well as its upregulation during mitochondrial stress suggests it might have an important survival function in the mitochondria by acting as a chaperone. To understand how HtrA2 acts as a protease, chaperone and regulator of apoptosis, an intricate dissection of its structure and dynamics and study of its interaction with its binding partners becomes imperative and we are exploring these aspects of the protease using biophysical, structural, proteomics and molecular biology probes. These studies will help us better understand the regulation of HtrA2 functions.
4. Understanding the mechanism of apoptosis regulation involving anti-apoptotic protein HAX1 and pro-apoptotic serine protease HtrA2/Omi
Recent studies have identified mitochondrial antiapoptotic Hax-1 protein as a binding partner cum substrate of HtrA2 suggesting its proapoptotic and proteolytic functions might converge. It has been observed that interaction of Omi with Hax-1 leads to Hax-1 degradation and subsequent activation of Omi showcasing an early event in apoptosis while Omi is still localized in the mitochondria. This mechanism of caspase- independent apoptosis regulation by Omi at the mitochondrial level is novel and hence demands further characterization. Here we are studying the Omi-Hax-1 complex using multidisciplinary tools with an aim to carry out structural analysis as well as to decipher the mechanism of Omi activation and its early regulation of apoptosis in the mitochondria.
Dr. Kakoli Bose, PI
Pandurang Padale, Lab Technician
Snehal Pandav Mudrale, Scientific Assistant
Nitu Singh, SRF
Lalith Kumar Chaganti, SRF
Raja Reddy Kuppili, SRF
Saujanya Acharya, JRF
Raghupati K, JRF
Ajay Wagh, JRF
Current Research Interns:
Opportunities: If any for students
• Chaganti LK, Kuppili RR, Bose K. (2013) Intricate structural coordination and domain plasticity regulate activity of serine protease HtrA2.FASEB J. 27(8), 3054-3066.
• Bejugam PR, Kuppili RR, Singh N, Gadewal N, Chaganti LK, Sastry GM, Bose K. (2013) Allosteric Regulation of Serine Protease HtrA2 through Novel Non-Canonical Substrate Binding Pocket. PLoS ONE 8(2): e55416.
• Singh N, Kuppili RR, Bose K. (2011)The structural basis of mode of activation and functional diversity: a case study with HtrA family of serine proteases16 (2), 85-96 : Review (Cover Page Publication)
• Bose K, Meinke G, Bohm A, Baleja JD. (2011). Design and characterization of an enhanced repressor of human papillomavirus E2 protein, FASEB J. 25(7). 2354 -2361
• Bose K, Yoder NC, Kumar K and Baleja JD. (2007). The Role of Conserved Histidines in the Structure and Stability of Human Papillomavirus Type 16 E2 DNA Binding Domain, Biochemistry. 46, 1402-1411
• Wei J, Liu Y,Bose K, Henry GD and Baleja JD. (2009). Disorder and Structure in the Rab-11 Binding Domain of Rab-11 Family Interacting Protein 2, Biochemistry 46, 549-557
• Bose K and Clark AC. (2005). pH Effects on the Stability and Dimerization of Procaspase-3. Protein Sci. 14, 24-36
• Bose K, Pop C, Feeney B, and Clark AC. (2003). An Uncleavable Procaspase-3 Mutant has a Lower Catalytic Efficiency but an Active Site Similar to That of Mature Caspase-3. Biochemistry 42, 12298-12310
• Bose K and Clark AC. (2001). Dimeric Procaspase-3 Unfolds via a Four-State Equilibrium Process. Biochemistry 40,14236-14242
• Pop C, Chen Y-R, Smith B, Bose K, Bobay B, Tripathy A, Franzen S and Clark AC. (2001). Removal of the Pro-domain Does Not Affect the Conformation of the Procaspase-3 Dimer. Biochemistry 40, 14224-14235
Links: 1. Lab Webpage: http://www.actrec.gov.in/pi-webpages/KakoliBose
2. Comprehensive PDZ (protein-protein interacting domain) database developed by IBSB Lab:http://www.actrec.gov.in:8080/Pdzome/jsp/Blast.jsp
Awards / Honors:
Life Member- Indian Biophysical Society, IACR
Member- Biophysical Society