All secreted proteins, and most that ultimately reside within the cell, must traverse the secretory pathway, a network of intracellular organelles housing the “machines” that help secreted proteins mature.Critical components of these machines are a class of proteins known as molecular chaperones, some of which are associated with the endoplasmic reticulum (ER). If, however, protein folding is inefficient or slow, a secreted protein may be targeted for destruction by a process we termed ER Associated Degradation, or ERAD. During ERAD, proteins are selected as being defective, are modified with ubiquitin, and are degraded by the proteasome, a multi-catalytic protease that resides in the cytoplasm. Molecular chaperones are required for ERAD by “deciding” whether a protein is sufficiently mature to transit through the secretory pathway. Molecular chaperones can also direct ERAD substrates to the proteasome. The importance ofunderstanding the molecular mechanism of ERAD and molecular chaperone action is underscored by the fact that several human diseases—including cystic fibrosis, heart and liver disease, diabetes, and neurodegenerative diseases—can arise from defects in chaperone-mediated folding of secreted proteins and/or the ERAD pathway.
For our studies, the Brodsky laboratory primarily utilizes a model eukaryotic organism, the yeast Saccharomyces cerevisiae (Figure 1). Yeast possess the same intracellular membrane organization and molecular chaperones as human cells but are amenable to rapid genetic analysis. Moreover, the basic machinery required for ERAD is completely conserved between yeast and humans. Current research in the Brodsky laboratory is directed toward understanding how molecular chaperones in the ER and the cytoplasm facilitate ERAD and protein folding in the cell. Human proteins expressed heterologously in yeast, such as CFTR (Figure 2), are being examined as substrates for ERAD and chaperone-mediated folding. Data derived from our genetic studies are complemented by biochemical assays that recapitulate specific steps in the ERAD pathway, and by studies using cells from higher organisms in which disease phenotypes are more relevant. In parallel, we have identified and characterized small molecule modulators of specific molecular chaperones, some of which have potent inhibitory effects on cancer cells and on the replication of human viruses.
Dr. Brodsky is also the Director of the Center for Protein Conformational Diseases (please see www.proteindiseasecenter.pitt.edu/about-our-center for additional information).
Students may find the Metabolic Pathways and Regulation (BIOSC1820) Course Website useful.
- Teresa Buck, Research Assistant Professor
- Annette Chiang, Post-doctoral research fellow
- Lynley Doonan, Graduate Student
- Sam Estabrooks, Graduate Student
- Jennifer Goeckeler-Fried, Lab Manager and Research Specialist
- Chris Guerriero, Research Assistant Professor
- Olivia Hillal, Undergraduate researcher
- Deepa Kumari, Graduate Student
- Timothy Mackie, Graduate Student
- Patrick G. Needham, Research Assistant Professor
- Danica Pratta, Undergraduate researcher
- George Preston, Post-doctoral associate
- Sara Sannino, Post-doctoral research fellow
- Andrew Schulz, Undergraduate researcher
- Zhihao Sun, Graduate Student