Alexander Strongin earned his PhD from Moscow State University in Russia in 1972 and his D.Sci. degree from the Institute of Microbial Genetics in Moscow in 1983. From 1982 to 1988, Dr. Strongin was head of the Laboratory of Functional Enzymology at the Institute of Genetics of Microorganisms in Moscow. He served as head of the Department of Biotechnology and Laboratory of Protein Engineering, Institute of Molecular Genetics, Russian Academy of Sciences, Moscow, from 1988 to 1990. From 1990 to 1994, he was a visiting professor of biochemistry in the Division of Dermatology at Washington University School of Medicine, St. Louis, Missouri. Dr. Strongin has worked in the La Jolla area since 1994, as senior staff scientist in the Biology Division at General Atomics, 1994-1995, and as senior staff scientist at the La Jolla Institute for Experimental Medicine, 1995-1999. Dr. Strongin joined Sanford Burnham Prebys on September 1, 1999.
Related Disease
Anthrax, Arthritis, Brain Cancer, Breast Cancer, Cancer, Hepatitis C, Multiple Sclerosis, Prostate Cancer, Type 1 Diabetes
Tumors produce unique enzymes, which by degrading the normal tissue provide an opportunity for tumor to grow in size and metastasize. These enzymes are called matrix metalloproteinases or MMPs. MMPs are a primary target for the design of anti-cancer pharmaceuticals. Our work aims to lay the foundation from which efficient therapeutics could ultimately be derived. Dr Strongin’s research is focused on the fundamental mechanisms involving MMPs in the processes of cell migration, cell proliferation and metastasis. The far-reaching goals of this pioneering research are to gain an understanding of how MMPs by cleaving the surrounding tissue and by affecting cell surface receptors govern locomotion of malignant cells. This knowledge is critical for design of efficient pharmaceuticals that may find applications in a variety of disease conditions including cancer, arthritis and stroke.
Alex Strongin’s Research Report
Degradation of the extracellular matrix and tissue remodeling play critical roles in tumor progression, particularly in invasion, metastasis, and neovascularization. Matrix metalloproteinases (MMPs) are essential for matrix proteolysis. Understanding the roles of MMPs in tumor growth and angiogenesis is of paramount importance to novel strategies for treatment of malignant tumors. Our primary goal is to characterize mechanisms of MMP activation involved in spatial and temporal control of focal proteolysis and to increase knowledge of cell-mediated matrix remodeling. Recently, we showed that heteromolecular assemblies involving MMPs and integrins that can simultaneously activate and dock MMPs are present on the surfaces of tumor cells. Apparently, these mechanisms of MMP activation are instrumental in clustering activated proteinases and integrins at the protrusions at the invasive front of migrating cells and at the invasive front of tumors (see Figure).
Interactions between MMPs and integrins, critical to spatial and temporal control of proteolysis, most likely are common for many cell types. To test our hypotheses and to outline novel approaches to control the activity of MMPs, we are examining mechanisms involved in activation, docking, and cross talk of MMPs and integrins in vivo and in vitro. We expect to experimentally show at the cell and protein sequence levels how the temporal and spatial regulation of matrix degradation is linked to dynamic changes of cell shape and cytoskeleton and to identify molecular mechanisms of cell motility. The immediate results of these studies will be improved diagnosis and treatment of malignant neoplasms.
Schematic depiction of the MMP-integrin molecular assembly. Inhibitory effects of tissue inhibitors of metalloproteinases (TIMPs) and the C-terminal domain of MMP-2 are shown by black arrows. The conversions of MMP-2 are shown by open arrows. The question mark stands for a cytoskeletal protein involved in a complex with membrane type-1 matrix metalloproteinase (MT1-MMP). This assembly is critical for docking, activation, and cross talk of MMPs and integrins and is intimately involved in regulating focalized matrix degradation and cell locomotion. MT1-MMP is in immediate proximity to integrin alpha vbeta 3. Both MT1-MMP and the integrin associate with the cytoskeleton. TIMP-2 links MT1-MMP (“a receptor”) and the secretory MMP-2 proenzyme. The second molecule of MT1-MMP (“an activator” that is free of TIMP-2) activates integrin alpha vbeta 3 by limited proteolysis of the beta 3 integrin subunit. The activator initiates the activation of pro-MMP-2 by cleaving the N-terminal part of the 68-kDa MMP-2 latent zymogen. The 64-kDa activation intermediate of MMP-2 efficiently associates with activated integrin alpha vbeta 3 via the C-terminal domain of the enzyme. The 64-kDa to 62-kDa autocatalytic maturation occurs if MMP-2 is complexed with the integrin. The mature MMP-2 enzyme transiently associated with the integrin at the surface of tumor cells accelerates the directional invasion of the cells. Additionally, if transiently complexed with the integrin at the surface of host stromal cells, the enzyme facilitates tumor neovascularization. TIMPs, including TIMP-2 and TIMP-1, efficiently inhibit the activity of soluble MMP-2. By providing links between integrins, MMPs, and TIMPs and, more generally, between cell shape and focal proteolysis, this model represents basic mechanisms of pro-MMP-2 activation and illustrates a coordinated interplay of inhibitors, proteinases, and integrin adhesion receptors at cell surfaces.
Arnold C. Satterthwait earned his PhD In Biochemistry with William Jencks from Brandeis University in 1973. He carried out postdoctoral research in Chemistry at Harvard University with Frank Westheimer, Imperial College with Alan Fersht and MIT with the Nobel laureate Gobind Khorana. In 1984, he joined The Scripps Research Institute in La Jolla, CA as an Assistant Professor. He moved to Sanford Burnham Prebys in 1998.
Related Disease
Anthrax, Breast Cancer, Cancer, HIV/AIDS, Prostate Cancer
The development of diagnostic reagents, drugs and vaccines is the visible outcome of a long process that spans the researcher’s laboratory and doctor’s office. The translation of disease discoveries into early detection, treatment, and prevention both tests and shapes our understanding of disease. Traditionally, drug companies have screened large collections of compounds against diseases to identify drugs. The Satterthwait lab seeks to take advantage of the explosion of new discoveries at the molecular level. We have developed synthetic methods that allow us to independently make and manipulate the critical three-dimensional regions of proteins that are being implicated in many diseases. These mini proteins are being used to assess new theories of disease at the molecular level to identify targets for various uses. We are currently using mini proteins to identify new antibodies (HIV-1), cancer drugs (prostate, breast and lung), and vaccines (anthrax).
Arnold Satterthwait’s Research Report
Peptide engineering relies on synthetic procedures to fold peptides into bioactive structures. It seeks to bridge a gap between chemistry and molecular biology by reducing the active sites of proteins to smaller molecules. Although synthetic peptides show occasional activity they are, unlike proteins, disordered and because of this often inactive. By refolding peptides into three-dimensional structures, they become active, opening up new avenues for studies on protein structure and function as well as providing leads for drugs and vaccines.
Solid-phase synthesis of a peptide constrained with a hydrazone covalent hydrogen bond mimic. The NMR structure of Sar-Ala-Ala-Gly (left) stabilized as a Type I turn (10% of protein structure) with an amidinium link (in black). The NMR structure of acetyl-Gly-Leu- Ala- Gly-Ala-Glu-Ala-Ala-Lys-Ala-amide (right) stabilized as an a-helix at its N-terminus with a hydrazone link (in black).
To fold peptides, we developed covalent hydrogen bond mimics. On average, greater than 60% of the amino acids in globular proteins engage in main-chain to main-chain hydrogen bonding (NH –> O=CRNH). In addition, protein substructures are defined by distinct hydrogen bonding patterns. Because hydrogen bonds are weak bonds, insufficient for stabilizing peptide structure, we replace them at structure defining positions in peptides with amidinium (N-C(R) = NH-CH2CH2) and hydrazone (N-N=CH-CH2CH2) covalent links. To simplify these transformations, we developed machine-assisted, multiple-peptide-synthesis procedures for inserting the hydrazone link into peptides which we link to automated multiple purifications. While these procedures, like peptide synthesis, remain labor intensive and often problematic, the critical problems have been breached.
Conformational analysis is as much a part of peptide engineering as synthesis because any claim to structure requires rigorous proof and further advances rely on understanding the relation between structure and chemistry. We have made considerable use of 2D NMR spectroscopy for structural analysis and calculations and with the help of collaborators, X-ray crystallography. These studies show unequivocally that covalent hydrogen bond mimics can stabilize peptides as b-turns, the a-helix, and even complex loops, which together make up the majority of protein substructures found on the surfaces of globular proteins.
Because protein substructure mimetics are now accessible, we have been examining the relationship between structure and activity by comparing the activities of peptides with substructure mimetics. From the several examples we have studied in detail, it is clear that remarkable gains in activity can be achieved.
