Daniel Gewirth, PhD

portrait of Daniel Gewirth.

Our Goal

Humans owe their existence to the proteins that reside in, on, and around every cell in the body. Proteins are useless, however, unless they are folded correctly into their active form. Proteins don’t last forever; they also get old and need to be disposed of properly. Failure at either end of the protein life cycle – folding at the beginning or disposal at the end – is a cellular catastrophe that leads inevitably to misfunction or death.

Recognizing the absolute importance of protein quality control, organisms have evolved a specialized class of proteins called chaperones. Chaperones help other proteins achieve their folded, active form or partition into the disposal system when they are old or damaged. Virtually every protein in the body at one time or another will interact with a member of the chaperone machinery, an indication of the importance placed on these mediators for cellular quality control. Diseases such as cancer, neurodegeneration, and infection, to name a few, are characterized by potentially lethal alterations to the amount and overall composition of the proteins in the cell. Paradoxically, the same chaperone systems that help maintain cellular order in normal cells are often co-opted by diseases to perpetuate the survival of diseased cells with altered protein burdens.

Drugs that selectively target individual members of the chaperone machinery offer great potential in the treatment of disease. The goal of the Gewirth lab is to understand these chaperone systems and to exploit these insights in the development of novel therapeutics.

A Deeper Understanding

Laboratory Research Interests:

  1. Structural studies of Hsp90 chaperones, drug design, protein folding.
  2. Steroid hormone receptors.

1. Structure-Function Studies of hsp90 chaperones. The hsp90 family of molecular chaperones are key players in the conformational maturation and folding of an extensive array of cellular client proteins ranging from steroid receptors to regulatory kinases, Toll-like receptors, G-proteins, telomerases and many others. Inhibitors of hsp90s, such as geldanamycin, are potent anti-tumor compounds because of their inhibitory effect on the maturation of clients that are key players in cellular transformation and malignancy, and are the subject of intense pharmacological interest. The mechanism by which hsp90 chaperones act to mature client proteins is still poorly understood. Over the past decade, our group has determined a series of structures of Grp94, the endoplasmic recticulum hsp90 paralog. Grp94 has a specialized but important portfolio of client proteins that include cell surface receptors, integrins, and growth factors. The structures we have determined have been of both the intact protein as well as its regulatory N-terminal domain, and have been solved in complex with a variety of inhibitory and naturally-occuring ligands. These structures and the associated biochemical and functional studies have revealed, among other highlights, a ligand-dependent switch in the N-terminal domain, unique conformational and quaternary states of the intact chaperone, a regulatory role for the extensive pre-N terminal portion of the molecule, and the mechanism by which Grp94 selectively binds to certain types of inhibitory ligands. These last insights are currently being exploited in the design and synthesis of novel Grp94 inhibitors, early versions of which have been shown to target HER2+ breast cancer cell lines. Grp94-selective compounds not only have therapeutic potential but should also prove useful for dissecting the cellular roles of the individual hsp90s. Recent structures of intact Grp94 have now begun to shed light on potential client binding interactions, and ongoing studies aim to deepen our understanding of this important mechanistic question.

2. Studies of the Androgen Receptor and characterization of novel AR inhbitors. The androgen receptor (AR) is the key cellular mediator of prostate cancer, the most common form of cancer to afflict western men after lung cancer. Late stage prostate cancers are often associated with androgen insensitivity, which renders standard castration and anti-androgen therapies ineffective. The androgen receptor is a transcription factor that binds to specific DNA targets. Our group has determined the structure of the AR DBD bound to a selective DNA target. The structure explains how AR forms the dimeric interactions that allow it to bind to these elements. Compounds that specifically interfere with the protein-protein or protein-DNA interactions constitute a new approach to anti-androgen therapy. Ongoing studies are also now examining the N-terminal activation domain of the receptor, which may form tertiary interactions with the other domains of the receptor and allow constituitive gene activation. This analysis should explain the hormone independent activity of the AR and may lead to the development of novel anti-androgens that do not target the mutagenically sensitive hormone binding domain.

Publications