Recognition and Accommodation at the Androgen Receptor Coactivator Binding Interface

Prostate cancer is a leading killer of men in the industrialized world. Underlying this disease is the aberrant action of the androgen receptor (AR). AR is distinguished from other nuclear receptors in that after hormone binding, it preferentially responds to a specialized set of coactivators bearing aromatic-rich motifs, while responding poorly to coactivators bearing the leucine-rich “NR box” motifs favored by other nuclear receptors. Under normal conditions, interactions with these AR-specific coactivators through aromatic-rich motifs underlie targeted gene transcription. However, during prostate cancer, abnormal association with such coactivators, as well as with coactivators containing canonical leucine-rich motifs, promotes disease progression. To understand the paradox of this unusual selectivity, we have derived a complete set of peptide motifs that interact with AR using phage display. Binding affinities were measured for a selected set of these peptides and their interactions with AR determined by X-ray crystallography. Structures of AR in complex with FxxLF, LxxLL, FxxLW, WxxLF, WxxVW, FxxFF, and FxxYF motifs reveal a changing surface of the AR coactivator binding interface that permits accommodation of both AR-specific aromatic-rich motifs and canonical leucine-rich motifs. Induced fit provides perfect mating of the motifs representing the known family of AR coactivators and suggests a framework for the design of AR coactivator antagonists

Survival of syngeneic and allogeneic iPSC–derived neural precursors after spinal grafting in minipigs

The use of autologous (or syngeneic) cells derived from induced pluripotent stem cells (iPSCs) holds great promise for future clinical use in a wide range of diseases and injuries. It is expected that cell replacement therapies using autologous cells would forego the need for immunosuppression, otherwise required in allogeneic transplantations. However, recent studies have shown the unexpected immune rejection of undifferentiated autologous mouse iPSCs after transplantation. Whether similar immunogenic properties are maintained in iPSC-derived lineage-committed cells (such as neural precursors) is relatively unknown. We demonstrate that syngeneic porcine iPSC-derived neural precursor cell (NPC) transplantation to the spinal cord in the absence of immunosuppression is associated with long-term survival and neuronal and glial differentiation. No tumor formation was noted. Similar cell engraftment and differentiation were shown in spinally injured transiently immunosuppressed swine leukocyte antigen (SLA)–mismatched allogeneic pigs. These data demonstrate that iPSC-NPCs can be grafted into syngeneic recipients in the absence of immunosuppression and that temporary immunosuppression is sufficient to induce long-term immune tolerance after NPC engraftment into spinally injured allogeneic recipients. Collectively, our results show that iPSC-NPCs represent an alternative source of transplantable NPCs for the treatment of a variety of disorders affecting the spinal cord, including trauma, ischemia, or amyotrophic lateral sclerosis

A Postmitotic Role for Isl-Class LIM Homeodomain Proteins in the Assignment of Visceral Spinal Motor Neuron Identity

AbstractLIM homeobox genes have a prominent role in the regulation of neuronal subtype identity and distinguish motor neuron subclasses in the embryonic spinal cord. We have investigated the role of Isl-class LIM homeodomain proteins in motor neuron diversification using mouse genetic methods. All spinal motor neuron subtypes initially express both Isl1 and Isl2, but Isl2 is rapidly downregulated by visceral motor neurons. Mouse embryos lacking Isl2 function exhibit defects in the migration and axonal projections of thoracic level motor neurons that appear to reflect a cell-autonomous switch from visceral to somatic motor neuron character. Additional genetic mutations that reduce or eliminate both Isl1 and Isl2 activity result in more pronounced defects in visceral motor neuron generation and erode somatic motor neuron character. Thus, an early phase of high Isl expression and activity in newly generated motor neurons permits the diversification of visceral and somatic motor neuron subtypes in the developing spinal cord

Interactions of FxxYF and FxxFF with the AR LBD

<p>FxxYF (A) and FxxFF (B) bound to the AR AF-2 interface. FxxYF and FxxFF are shown as yellow and orange Cα coils, respectively. The LBD is depicted as in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0020274#pbio-0020274-g003" target="_blank">Figure 3</a>.</p

Interactions of the Tryptophan Motifs with the AR LBD

<p>FxxLW (A), WxxLF (B), and WxxVW (C) bound to the AR AF-2 interface. FxxLW, WxxLF, and WxxVW are shown as orange, beige, and purple Cα coils, respectively. The LBD is depicted as in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0020274#pbio-0020274-g003" target="_blank">Figure 3</a>.</p

Surface Complimentarity of Hydrophobic Motifs in the AR, ERα, and GR AF-2 Clefts

<p>(A) AR–FxxLF, (B)AR–LxxLL, (C) ERα–GRIP1 (LxxLL) (<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0020274#pbio-0020274-Shiau1" target="_blank">Shiau et al. 1998</a>), and (D) GR-TIF2 (LxxLL) (<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0020274#pbio-0020274-Bledsoe1" target="_blank">Bledsoe et al. 2002</a>). The inside surfaces of the AF-2 cleft in AR, ERα, and GR are depicted. The LBD is additionally shown as a Cα trace with key side chains shown as white sticks. Phenylalanines and leucines of the FxxLF and LxxLL motifs are shown as spheres.</p

A Structural Profile of the AR Coactivator Binding Interface

<div><p>AR–peptide complexes are colored as follows: FxxLF, yellow; FxxLW, orange; WxxLF, wheat; WxxVW, purple; FxxYF, green; FxxFF, blue; LxxLL, pink; unbound, grey.</p> <p>(A) Cα trace of the peptides superimposed onto the AF-2. For clarity only the LBD of AR–FxxLF is shown.</p> <p>(B) Superposition of the LBD of the AR–peptide complexes in the region of the coactivator interface. Backbone atoms are shown as a Cα trace. Side chains of residues composing the interface are shown as sticks.</p> <p>(C) Hydrophobic side chains of the core motif superimposed as in (B).</p></div