The American Cancer Society's 2012 report revealed that incidence rates are decreasing or stable for most cancers in the United States since 1999. Some notable exceptions are liver cancer in African Americans and Hispanics, endometrial cancer in African American women, colorectal cancer in patients under 50, and pancreatic cancer in every demographic. In all these tissues, NR5A nuclear receptors (NR5A1 and NR5A2) mediate genetic programs that are essential determinants of development, differentiation and adult function. At the molecular level, these two transcription factors bind phosphoinositides (PIPs), phospholipids that are essential to PI-3 kinase signaling in PTEN-dependent cancers. However almost nothing is known about how these lipids regulate NR5A transcriptional functions, or how dysregulation of those mechanisms contributes to the cancers mentioned above. Based on a manuscript currently in revision at Science, we hypothesize that PIP lipids bound to NR5As (and other nuclear proteins) are directly remodeled by the PI3- kinase inositol polyphosphate multikinase (IPMK) and the PTEN lipid phosphatase in cancer cells. This hypothesis is a clear departure from the standard dogma that PI3- kinases &PTEN only act on phosphoinositides in membranes.
In Aim 1, we will determine how currently available small molecules inhibit IPMK using enzymology and crystallography, accelerating improvements of these inhibitors and training the PI in crystallography, X-ray diffraction methods and molecular structure determination, taking advantage of a relatively low-risk project.
In Aim 2, we will use mutational analyses to map the interface between NR5A1 and IPMK, and attempt to crystallize NR5A/PIP/IPMK to determine the interfacial structure of this complex. This high-risk high-reward structure is hedged by Aim 1.
In Aim 3, we will identify novel protein/PIP complexes that are substrates of PTEN and IPMK, using hypothesis-driven biochemistry. The candidate has had extensive training in protein chemistry, enzymology, biochemistry and cell biology, but has not had any training in structural biology. The mentor Holly Ingraham and advisory team have extensive experience in structural biology, particularly Robert Fletterick in NR5A structure and its links to pancreatic cancer, and Natalia Jura in kinase structure and membrane cancer biology. The candidate will expand his research program as an independent investigator with the training afforded by this K01 award, opening new avenues to cancer research.
A fundamental challenge to developing anti-cancer agents is the identification of tumor-specific, highly druggable targets that can be pursued pharmacologically to kill cancer cells and to extend what we know about biology and how cells work. This proposal identifies nuclear protein/lipid complexes as a new class of specific substrates for enzymes well established to be critical to oncogenesis and cancer progression. Collectively, our research should help target these tertiary protein/lipid/enzyme complexes by identifying 1) more of them and 2) providing molecular and atomic-level details about how they work, allowing them to be interfered with pharmacologically.
|Malabanan, M Merced; Blind, Raymond D (2016) Inositol polyphosphate multikinase (IPMK) in transcriptional regulation and nuclear inositide metabolism. Biochem Soc Trans 44:279-85|
|Sablin, Elena P; Blind, Raymond D; Uthayaruban, Rubatharshini et al. (2015) Structure of Liver Receptor Homolog-1 (NR5A2) with PIP3 hormone bound in the ligand binding pocket. J Struct Biol 192:342-8|
|Blind, Raymond D (2014) Disentangling biological signaling networks by dynamic coupling of signaling lipids to modifying enzymes. Adv Biol Regul 54:25-38|
|Blind, Raymond D; Sablin, Elena P; Kuchenbecker, Kristopher M et al. (2014) The signaling phospholipid PIP3 creates a new interaction surface on the nuclear receptor SF-1. Proc Natl Acad Sci U S A 111:15054-9|