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Michael Czech, Ph.D.
Academic Role: Professor
Faculty Appointment(s) In:
Program in Molecular Medicine
Joint Faculty In:
Biochemistry and Molecular Pharmacology
Other Affiliation(s):
Center for AIDS Research
Interdisciplinary Graduate Program
RNAi-based therapeutic strategies for inflammatory and metabolic diseases
Many major human diseases such as diabetes, atherosclerosis and rheumatoid arthritis are promoted by dysfunctions in inflammatory pathways. Macrophages are central players in such diseases based on their ability to express antigenic peptides on their cell surfaces and secrete cytokines that attract and activate immune cells. Experiments in our laboratory are currently devoted to 1.) applying RNAi-based approaches to identify target genes in macrophages, adipocytes and other cells that promote these diseases, and 2.) developing strategies for therapeutic application of RNAi against these targets.
Unlike small molecule drugs, RNAi can target human genes without regard to the nature of the protein structure of the gene product. As a consequence, all genes become potential targets for RNAi based therapies. However, there is one over-riding roadblock to the general use of siRNA as a medicine for human disease: safe, effective delivery to specific target tissues or cell types in vivo. Achieving the goal of an oral delivery system for synthetic siRNA, in particular, could potentially transform the practice of medicine.
Our laboratory is engaged in collaborative experiments with Dr. Gary Ostroff’s group to achieve orally delivered siRNA as an effective therapeutic strategy for inflammatory pathways. We are employing unique encapsulation technology that both protects siRNA through the digestive tract and directs its uptake by macrophages and dendritic cells where it silences genes involved in pathogenic inflammation.
Other projects in our laboratory address the underlying mechanisms whereby inflammation and other processes impair insulin signaling in obesity and type 2 diabetes. We are investigating the roles of lipid droplet proteins in regulating adipocyte metabolism and whole body glucose tolerance using mouse knockout models and adipose samples from human subjects. Our studies are also directed towards understanding the signaling pathways whereby the protein kinase Map4k4 acts to cause insulin resistance. Finally, we are using high resolution ultrafast TIRF microscopy to study the cellular trafficking pathways whereby insulin controls the glucose transporter protein (GLUT4) that mediates glucose disposal in skeletal muscle and adipose tissue.
Figure Legend
Hypothesis: The protein kinase Map4k4 promotes insulin resistance by mediating cytokine production in macrophages and insulin resistance in adipocytes and skeletal muscle.
We discovered the protein kinase Map4k4/NIK as a negative regulator of insulin signaling and adipogenesis by employing an RNAi screen in mouse adipocytes (PNAS 103; 2087-2092, 2006). Map4k4 appears to be a mediator of some effects of the TNF-a signaling pathway, and is a negative regulator of PPARg expression in adipocytes. Subsequently, a paper appeared indicating the Map4k4 is also a negative regulator of insulin signaling in skeletal muscle of type 2 diabetics (J. Biol. Chem. 282; 7783-7789, 2007). We have more recently discovered that Map4k4 mediates cytokine expression and secretion in macrophages. Thus this protein kinase represents an exciting potential therapeutic target for inflammatory diseases and diseases where macrophages play a pathogenic role, e.g., diabetes, atherosclerosis, rheumatoid arthritis and inflammatory bowel diseases.
Representative Publications
Guilherme A, Virbasius JV, Puri V, Czech MP. Adipocyte dysfunctions linking obesity to insulin resistance and type 2 diabetes.Nat Rev Mol Cell Biol. 2008; May; 9(5):367-77.
Puri V, Ranjit S, Konda S, Nicoloro SM, Straubhaar J, Chawla A, Chouinard M, Lin C, Burkart A, Corvera S, Perugini RA, Czech MP. Cidea is associated with lipid droplets and insulin sensitivity in humans.Proc Natl Acad Sci U S A. 2008; Jun 3; 105(22):7833-8.
Huang S, Czech MP. The GLUT4 glucose transporter.Cell Metab. 2007; Apr; 5(4):237-52.
Czech MP. MicroRNAs as therapeutic targets.N Engl J Med. 2006; Mar 16; 354(11):1194-5.
Mello CC, Czech MP. Micromanaging insulin secretion.Nat Med. 2004; Dec; 10(12):1297-8.
Czech MP. Fat targets for insulin signaling.Mol Cell. 2002; Apr; 9(4):695-6.
Bose A, Guilherme A, Robida SI, Nicoloro SM, Zhou QL, Jiang ZY, Pomerleau DP, Czech MP. Glucose transporter recycling in response to insulin is facilitated by myosin Myo1c.Nature. 2002; Dec 19-26; 420(6917):821-4.
Czech MP. PIP2 and PIP3: complex roles at the cell surface.Cell. 2000; Mar 17; 100(6):603-6.
Rotation Projects
There are several available rotation projects in the laboratory for graduate students. Examples are outlined below:
Oral delivery of siRNA as a therapeutic strategy for types 1 and 2 diabetes
The autoimmune reactions that cause destruction of beta cells and type 1 diabetes are driven by autoreactive T cells in association with innate inflammatory cells (macrophages and dendritic cells). Paradoxically, recent research indicates these latter cells in the immature state also play key roles in establishing immunological tolerance, through presentation of antigens to T cells within a "tolerogenic" context. One of the most promising concepts that has emerged from these studies is that induction of immunological tolerance to beta cell auto-antigens might prevent or even alleviate the disease. Immunological tolerance has many forms and mechanisms, but a major paradigm is the generation of regulatory T cells (T-regs) by tolerogenic macrophages or dendritic cells that suppress the cascade of events leading to auto-reactivity and beta cell apoptosis. These events appear to take place in the local regions of the islets and nearby lymph nodes. Further, the gut-associated lymphatic system represents a key site where induction of immunological tolerance may be critically important. This collaborative research project with Gary Ostroff's laboratory is based on our discovery that siRNA encapsulated within micron-sized, hollow shells of beta 1,3-D-glucan can be delivered orally to mice to target dendritic cells and macrophages in the gut. This technology advance enables us to integrate two approaches that might promote immunological tolerance to prevent or alleviate type 1 diabetes: 1) tolerize the gut immune system to beta cell antigens through targeted antigen delivery to dendritic cells and macrophages in the gut; 2) orally deliver RNAi to silence genes that control the secretion of proinflammatory cytokines, co-stimulatory receptors or "maturity" factors in dendritic cells and macrophages during the early stages of beta cell antigen presentation to induce T-reg and hypo-responsive T cells. Type 2 diabetes in obesity is also associated with an inflammation phenotype-in this case within adipose tissue. Thus, we have also initiated experiments to target macrophages in obese mouse models of type 2 diabetes with orally delivered siRNA directed against genes that control inflammation. Rotation projects in the Czech laboratory applying oral delivery of encapsulated siRNA to mouse models of both types 1 and 2 diabetes are now available to graduate students.
Lipid Droplet Proteins and their Roles in Fat Deposition in Obesity and Diabetes
Fat homeostasis is perturbed in type II diabetes and obesity and is a major factor associated with pathogenesis of metabolic diseases. High concentrations of circulating fatty acids and triglyceride, observed in both obesity and lipodystrophy, are thought to cause muscle insulin resistance and decreased glucose tolerance. Adipocytes could protect muscle and liver from these deleterious effects of fatty acids by their large capacity to esterify them into triglyceride, and to sequester large amounts of the triglyceride within lipid droplets. We have recently identified a set of novel proteins, Cidea and fat specific protein 27 (FSP27; also known as Cidec), which are associated with lipid droplets in adipocytes and their expression can enhance the accumulation of triglycerides in adipocytes both in vivo and in vitro (JBC 282: 34213-8, 2006; PNAS 105: 7833-8, 2008; Acta Physiologica 192: 103-115, 2008). Strikingly, Cidea and FSP27 expression was higher in insulin sensitive vs. resistant obese humans. Our studies indicate that Cidea and FSP27 define a novel, highly regulated pathway of triglyceride accumulation in mouse and human white adipose tissue and their expression is associated with insulin sensitivity in humans (JCI 118: 2693-6, 2008; Nature Reviews MCB 9, 367-77, 2008). Rotation projects in the laboratory are designed to address the mechanisms by which Cidea and FSP27 associate with lipid droplets and regulate triglyceride deposition. Currently, these projects utilize adipocytes in culture or from mice and human patients. Lipid droplets and associated proteins are analyzed by live cell microscopy and by cell and molecular biology techniques.
Insulin and Map4k4 Signaling and Adipogenesis Regulation
Insulin resistance in muscle is a major syndrome in obese humans that contributes to the onset of type 2 diabetes. The development of obesity coincides with substantial infiltration of macrophages into adipose tissue, which is associated with increased expression of inflammatory cytokines such as TNFa; (Nat Rev Mol Cell Biol. 5: 367-377, 2008). The nuclear receptor peroxisome proliferator-activated receptor g(PPAR g ) is a ligand-dependent transcription factor that acts as a primary regulator of adipogenesis and controls adipocyte metabolism and insulin action. Increased expression of TNFa; in adipose tissue of obese subjects potently suppresses the expression of PPARg; and attenuates adipocyte functions.
We screened cultured adipocytes with siRNA directed against over two hundred protein kinases for negative regulators of insulin-sensitive glucose transport. Among several hits in this screen, we discovered the mitogen-activated protein kinase 4 (MAP4k4) as a protein kinase of the Ste20 family that exhibits potent inhibitory effects on insulin sensitivity and adipogenesis (Proc. Natl. Acad. Sci. USA 103: 2087, 2006). Remarkably, silencing Map4k4 caused an increase in the expression of peroxisome proliferator-activated receptor; g(PPARg ), along with a corresponding increase in the expression of GLUT4 and stimulation of insulin-mediated deoxyglucose uptake. More recent studies have shown that MAP4K4 mediates the insulin resistance in muscle induced by TNF-a; (J Biol Chem. 282: 7783-7789, 2007). Interestingly, TNF-a; both increases Map4k4 acute catalytic activity and Map4k4 expression in adipocytes through activation of TNF-a -receptor 1 (TNFR1), but not TNFR2. (Proc. Natl. Acad. Sci. USA 103: 2087, 2006; J Biol Chem., 282:19302-19312). An important question that is currently under investigation in our laboratory is what are the molecular mechanisms by which MAP4K4 upregulates PPAR function? We found that RNAi-mediated silencing of MAP4K4 elevated the levels of both PPAR 1 and PPAR 2 proteins 2-3 fold in 3T3-L1 adipocytes without affecting PPAR mRNA levels, suggesting that MAP4K4 regulates PPARg at a post-transcriptional step. Moreover, silencing MAP4K4 had no effect on PPARg; degradation. However, depletion of MAP4K4 significantly enhances [S-35]-incorporation into proteins, suggesting that silencing of MAP4K4 increases protein translation. Based on our preliminary results, it appears that MAP4K4 regulates PPARg; protein expression by inhibiting mTOR-mediated protein translation. Rotation projects in the laboratory are designed to identify the elements downstream of the MAP4K4 signaling pathways that mediate its effects on protein translation in cultured adipocytes.
Inflammation in Adipose Tissues of Obese Human Subjects
Obesity is an independent risk factor for multiple medical conditions. Interestingly, not all obese individuals manifest obesity-related comorbidities, highlighting the importance of identifying specific genetic and biological factors that place a subset of obese individuals at the greatest risk for complications. We are collaborating with Dr. Richard Perugini in the Department Surgery on this topic. With the goal of elucidating the molecular mechanisms of insulin resistance in obesity we compared differences in gene expression in intra-abdominal and subcutaneous adipose tissue from obese patients undergoing gastric bypass surgery. Using Affymetrix GeneChip profiling we identified three gene sets (chemokine activity, chemokine receptor binding, g-protein couple receptor binding) that were upregulated in omental tissue from insulin resistant patients compared to BMI-matched insulin sensitive patients. Differential expression of seven genes common to all three gene sets (CCL2, CCL3, CCL4, CCL8, CXCL2, CXCL10, IL8) was confirmed with RTqPCR and showed a clear association with insulin resistance. The omental adipose tissue from insulin resistant subjects also demonstrated adipocyte hypertrophy and increased macrophage infiltration compared to omental tissue from insulin sensitive subjects. These exciting results showing that elevated chemokine expression in omental adipose tissue is associated with insulin resistance and adipose inflammation in obese human subjects of equal BMI values raise several important questions: Which cell type is responsible for the chemokine production and secretion? Are other immune cells involved in this inflammatory process? Do serum levels of chemokines increase in the insulin resistant state? Does the inflammation in adipose tissue we observe cause insulin resistance in skeletal muscle in these patients? These questions can be solved utilizing a variety of techniques including fractionation of whole adipose tissue, immunohistochemistry, and serum analysis using Cytometric Bead Analysis. Rotation students will be able to pursue studies of this type in our laboratory.
Laboratory Members
- Research Assistant Professors:
- Anil Chawla, PhD, Adilson Guilherme, PhD, Jack Huang, PhD, Zhen Yue Jiang, MD/PhD, Joseph Virbasius, PhD
- Instructors:
- Qionglin Zhou, PhD, Avirup Bose, PhD
- Postdoctoral Fellows:
- Sabina Semiz, PhD, Xiaqing Tang, PhD, Chuanyou Zhang, PhD
- Technical Associates:
- Sarah Nicoloro, John Holik, Darcy Pomerleau, Stacey Robida, Neil Soriano
- Graduate Students:
- Jingyoon Park, PhD, Ken Bishop, MD/PhD
Academic Background
Michael P. Czech is Professor and founding Chair of the Program in Molecular Medicine, University of Massachusetts Medical School. Molecular Medicine currently includes 37 faculty research laboratories, several Howard Hughes Investigators and over 400 scientists and staff. His research addresses mechanisms of signal transduction and insulin resistance in type 2 diabetes and obesity. His laboratory has recently applied RNAi to discover novel drug targets and to develop therapeutic strategies for alleviating inflammatory and metabolic diseases.
Dr. Czech earned the PhD degree in biochemistry in 1972 at Brown University, and completed postdoctoral study at Duke University Medical Center. He became Assistant Professor at Brown in 1974, rising to the rank of Professor in 1980. In 1981 Dr. Czech moved to the University of Massachusetts Medical School as Professor and Chair of the Department of Biochemistry and Molecular Pharmacology, which he led until his appointment as Director of Molecular Medicine in 1989.
Dr. Czech has authored approximately 275 publications, serves on several editorial boards, and has served on several NIH Study Sections and Review Panels of the Howard Hughes Medical Institute. He has received the Outstanding Scientific Achievement Award of the American Diabetes Association, 1982; the David Rumbough Scientific Award of the Juvenile Diabetes Foundation in 1985; an NIH MERIT Award, 1997-2005; the Elliot P. Joslin Medal in 1998, the 2000 CIIT Founder’s Award, the 2000 Banting Medal and the 2004 Albert Renold Award of the American Diabetes Association.
Office: Suite 100
Phone: 508-856-2254
Fax: 508-856-1617
E-mail: Michael.Czech@umassmed.edu
Keywords:
Signal Transduction,
Cell Biology,
Biochemistry
Postdoctoral Position Available
A postdoctoral position is available to study in this laboratory.
Contact Dr. Czech for additional details.
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364 Plantation Street Worcester, MA 01605