Alexey S. Ladokhin, Ph.D.

Professor
Department of Biochemistry and Molecular Biology

1979-1984: Shevchenko National University, Kyiv, Ukraine, B.S., Physics.
1984-1989: Institute of Biochemistry, NANU, Kyiv, Ukraine, Ph.D., Biophysics.
1990-1992: University of Virginia, Charlottesville, VA, Postdoctoral Fellow.
1992-1994: The Johns Hopkins University, Baltimore, MD, Postdoctoral Fellow.
1994-2004: University of California, Irvine, CA, Research Scientist
2004-2008: University of Kansas Medical Center, Kansas City, KS, Department of Biochemistry and Molecular Biology, Assistant Professor
2008-2018: University of Kansas Medical Center, Kansas City, KS, Department of Biochemistry and Molecular Biology, Associate Professor
2013-2014: University of California, Irvine, CA. Visiting Associate Professor.
2018 - present: University of Kansas Medical Center, Kansas City, KS, Department of Biochemistry and Molecular Biology, Professor

Interests: Membrane proteins in apoptotic regulation and cancer targeting, Bcl-2 proteins, bacterial toxins, antimicrobial peptides, biophysical techniques.

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Publications: Click here

University of Kansas Medical Center
aladokhin@kumc.edu

Major Research Interest

I. Conformational switching in apoptotic regulators of Bcl-2 family

Apoptosis is crucial for proper development and function of cell populations  in tissues, and its dysregulation impacts many diseases. Hyperactive apoptosis contributes to neurodegeneration and immunodeficiency, while insufficient apoptosis leads to autoimmunity and cancer, and the ability of cancer cells to avoid apoptosis significantly complicates treatment. The critical step in triggering apoptosis is the permeabilization of the mitochondrial outer membrane (MOMP), which releases apoptotic factors into the cytosol that lead to cell death. MOMP is controlled and executed by the numerous proteins of Bcl-2 family, which include three types (Fig. 1): pro-apoptotic pore formers (e.g., Bax), anti-apoptotic pore inhibitors (e.g., Bcl-xL), and BH3-only regulators (e.g., Bid).  These proteins directly interact within the mitochondrial outer membrane (MOM) either to promote or prevent protein conformational changes that lead to formation of an oligomeric pore. Our goal is to understand molecular mechanisms of membrane-induced conformational switching in Bcl-2 proteins in regulation of apoptosis.

II. Targeting cancer cells using pH-dependent refolding/insertion of diphtheria toxin translocation (T) domain.

Changes in side chain protonation are among the most prominent physicochemical  signals capable of triggering
functionally relevant structural rearrangements. For example, pH-dependent conversion of a protein structure from a water-soluble to membrane-inserted form is a key step in many processes, including cellular entry of bacterial toxins, colicins, and viruses, as well as membrane-mediated regulation of apoptosis by the Bcl-2 family of proteins, critical for cancer treatment.  Remarkably, the protonation phenomenon is also central to efforts to target acidic cancer tissues and other maladies.  We propose to combine these two aspects of the protonation by retargeting diphtheria toxin translocation (T) domain to deliver drugs into cancer cells via proton-induced conformational switching (e.g., see pH-dependent argeting of HeLa cells in Fig. 2). This project focuses on deciphering the molecular mechanism of pH-dependent refolding and membrane insertion of the diphtheria toxin T-domain, which is considered to be a paradigm for cell entry of other bacterial toxins (e.g., tetanus and botulinum) and has a potential for targeted delivery of anti-cancer therapies. Understanding the pH-triggered insertion of the T-domain will also reveal general physicochemical principles underlying membrane protein assembly and signaling on membrane interfaces.

The pH-low insertion peptide (pHLIP) is an important tool for drug delivery  and visualization of acidic tissues produced by various maladies, including cancer, inflammation, and ischemia.  Numerous studies indicate that pHLIP exists in three states: unfolded and soluble in water at neutral pH (State I), unfolded and bound to the surface of a phosphatidylcholine membrane at neutral pH (State II), and inserted across the membrane as an α-helix at low pH (State III). Recently we have reported how changes in lipid composition modulate this insertion scheme by modifying interfacial state and modulating the pKa of the insertion transition (Fig. 3). 

III. Membrane action of host-defense (antimicrobial and toxic) peptides

IV. Biophysical methods: Fluorescence Spectroscopy (FCS, FRET, lifetime spectroscopy, depth-dependent fluorescence quenching in membranes); Molecular Dynamics (MD) computer simulations.    

Ladokhin Lab - 2017	Ladokhin Lab 2014
Ladokhin Lab 2013	Ladokhin Lab 2012
Ladokhin Lab 2008