KL2 scholars' perceptions of factors contributing to sustained translational science career success

Introduction

Identifying the most effective ways to support career development of early stage investigators in clinical and translational science should yield benefits for the biomedical research community. Institutions with Clinical and Translational Science Awards (CTSA) offer KL2 programs to facilitate career development; however, the sustained impact has not been widely assessed.

Methods

A survey comprised of quantitative and qualitative questions was sent to 2144 individuals that had previously received support through CTSA KL2 mechanisms. The 547 responses were analyzed with identifying information redacted.

Results

Respondents held MD (47%), PhD (36%), and MD/PhD (13%) degrees. After KL2 support was completed, physicians' time was divided 50% to research and 30% to patient care, whereas PhD respondents devoted 70% time to research. Funded research effort averaged 60% for the cohort. Respondents were satisfied with their career progression. More than 95% thought their current job was meaningful. Two-thirds felt confident or very confident in their ability to sustain a career in clinical and translational research. Factors cited as contributing to career success included protected time, mentoring, and collaborations.

Conclusion

This first large systematic survey of KL2 alumni provides valuable insight into the group's perceptions of the program and outcome information. Former scholars are largely satisfied with their career choice and direction, national recognition of their expertise, and impact of their work. Importantly, they identified training activities that contributed to success. Our results and future analysis of the survey data should inform the framework for developing platforms to launch sustaining careers of translational scientists.

The National Cancer Institute R25 Cancer Education Grants Program: A Workshop Report

Through the R25 Cancer Education Grants Program (CEGP), the National Cancer Institute (NCI) has been supporting the broad educational needs of the cancer research and cancer healthcare communities since 1974. NCI sponsored a workshop on September 13, 2016 in Bethesda, Maryland, with the objectives of sharing best practices in cancer education, communicating R25 CEGP programmatic information, and gathering ideas to strengthen the R25 CEGP to better meet the emerging needs in cancer education in the face of a rapidly changing landscape in cancer research and cancer care. With 53 leaders in cancer education in attendance, the workshop featured an overview of the R25 CEGP by NCI Program Staff, a showcase of several types of CEGP programs by current R25 grantees, and in-depth discussions on a broad range of questions critical for the continued success of the R25 CEGP. The workshop afforded an opportunity, for the first time, for cancer researchers and clinicians conducting different forms of cancer education activities to gather in one place as leaders of a community of increasing importance. The discussion resulted in a set of suggestions that will benefit the R25 CEGP and cancer education in general. There was a general consensus among the participants that bringing the cancer education community together is a significant achievement of the workshop that will have a long-lasting impact on cancer education.

Regulation of M₃ muscarinic receptor expression and function by transmembrane protein 147

The M₃ muscarinic acetylcholine receptor (M3R) regulates many fundamental physiological functions. To identify novel M3R-interacting proteins, we used a recently developed yeast two-hybrid screen (split ubiquitin method) to detect interactions among membrane proteins. This screen led to the identification of many novel M3R-associated proteins, including the putative membrane protein transmembrane protein 147 (Tmem147). The amino acid sequence of Tmem147 is highly conserved among mammals, but its physiological roles are unknown at present. We initially demonstrated that Tmem147 could be coimmunoprecipitated with M3Rs in cotransfected mammalian cells (COS-7 cells). Confocal imaging studies showed that Tmem147 was localized to endoplasmic reticulum (ER) membranes and that the Tmem147/M3R interaction occurred in the ER of cotransfected COS-7 cells, resulting in impaired trafficking of the M3R to the cell surface. To study the role of Tmem147 in modulating M3R function in a more physiologically relevant setting, we carried out studies with H508 human colon cancer cells that endogenously express M3Rs and Tmem147. Treatment of H508 cells with carbachol, a hydrolytically stable acetylcholine analog, promoted H508 cell proliferation and activation of the mitogenic kinase, p90RSK. Small interfering RNA-mediated knockdown of Tmem147 expression significantly augmented the stimulatory effects of carbachol on H508 cell proliferation and p90RSK activation. These effects were associated with an increase in the density of cell surface M3Rs. Our data clearly indicate that Tmem147 represents a potent negative regulator of M3R function, most likely by interacting with M3Rs in an intracellular compartment (ER). These findings may lead to new strategies aimed at modulating M3R activity for therapeutic purposes.

Structural basis of the selectivity of the beta(2)-adrenergic receptor for fluorinated catecholamines

The important and diverse biological functions of adrenergic receptors, a subclass of G protein-coupled receptors (GPCRs), have made the search for compounds that selectively stimulate or inhibit the activity of different adrenergic receptor subtypes an important area of medicinal chemistry. We previously synthesized 2-, 5-, and 6-fluoronorepinehprine (FNE) and 2-, 5-, and 6-fluoroepinephrine (FEPI) and found that 2FNE and 2FEPI were selective beta-adrenergic agonists and that 6FNE and 6FEPI were selective alpha-adrenergic agonists, while 5FNE and 5FEPI were unselective. Agonist potencies correlated well with receptor binding affinities. Here, through a combination of molecular modeling and site-directed mutagenesis, we have identified N293 in the beta(2)-adrenergic receptor as a crucial residue for the selectivity of the receptor for catecholamines fluorinated at different positions.

Molecular Basis for the Differential Agonist Affinities of Group III Metabotropic Glutamate Receptors

Agonist stimulation of group III metabotropic glutamate receptors (mGluRs) induces an inhibition of neurotransmitter release from neurons. The group III mGluRs are pharmacologically defined by activation with the glutamate analog L-amino-4-phosphonobutyric acid (L-AP4). The affinities of these receptors for L-AP4 and glutamate vary over approximately a 1500-fold concentration range. The goal of this study was to elucidate the molecular basis for this dispersion of agonist affinities for the group III receptors mGluR4, mGluR6, and mGluR7. [3H]L-AP4 binding was present in human embryonic kidney cells transfected with the high-affinity mGluR4 receptor but not in cells transfected with mGluR6 or the low-affinity mGluR7 receptor. Analysis of mGluR4/mGluR6 receptor chimeras revealed that replacement of the first 35 amino acids of mGluR6 with the first 50 amino acids of mGluR4 was sufficient to impart [3H]L-AP4 binding to mGluR6. Homology models of mGluR4 and mGluR7 were used to predict amino acids that may affect ligand affinity. Mutations were made in mGluR7 to convert selected residues into the equivalent amino acids present in the high-affinity mGluR4 receptor. The mGluR7 N74K mutation caused a 12-fold increase in affinity in a functional assay, whereas the N74K mutation in combination with mutations in residues 258 to 262, which lie outside the binding pocket, caused a 112-fold increase in affinity compared with unmutated mGluR7. Our results demonstrate that the binding site residues at position lysine 74 in mGluR4, glutamine 58 in mGluR6, and asparagine 74 in mGluR7 are key determinants of agonist affinity and that additional residues situated outside of the binding pocket, including those present in the extreme amino terminus, also contribute to agonist affinity and the pharmacological profiles of the group III mGluRs.

Molecular determinants of high affinity binding to group III metabotropic glutamate receptors

The amino-terminal domain containing the ligand binding site of the G protein-coupled metabotropic glutamate receptors (mGluRs) consists of two lobes that close upon agonist binding. In this study, we explored the ligand binding pocket of the Group III mGluR4 receptor subtype using site-directed mutagenesis and radioligand binding. The selection of 16 mutations was guided by a molecular model of mGluR4, which was based on the crystal structure of the mGluR1 receptor. Lysines 74 and 405 are present on lobe I of mGluR4. The mutation of lysine 405 to alanine virtually eliminated the binding of the agonist [(3)H]l-amino-4-phosphonobutyrate ([(3)H]l-AP4). Thus lysine 405, which is conserved in all eight mGluRs, likely represents a fundamental recognition residue for ligand binding to the mGluRs. Single point mutations of lysines 74 or 317, which are not conserved in the mGluRs, to alanine had no effect on agonist affinity, whereas mutation of both residues together caused a loss of ligand binding. Mutation of lysine 74 in mGluR4, or the analogous lysine in mGluR8, to tyrosine (mimicking mGluR1 at this position) produced a large decrease in binding. The reduction in binding is likely due to steric hindrance of the phenolic side chain of tyrosine. The mutation of glutamate 287 to alanine, which is present on lobe II and is not conserved in the mGluR family, caused a loss of [(3)H]l-AP4 binding. We conclude that the determinants of high affinity ligand binding are dispersed across lobes I and II. Our results define a microenvironment within the binding pocket that encompasses several positively charged amino acids that recognize the negatively charged phosphonate group of l-AP4 or the endogenous compound l-serine-O-phosphate.

A YAC mouse model for Huntington's disease with full-length mutant huntingtin, cytoplasmic toxicity, and selective striatal neurodegeneration

We have produced yeast artificial chromosome (YAC) transgenic mice expressing normal (YAC18) and mutant (YAC46 and YAC72) huntingtin (htt) in a developmental and tissue-specific manner identical to that observed in Huntington's disease (HD). YAC46 and YAC72 mice show early electrophysiological abnormalities, indicating cytoplasmic dysfunction prior to observed nuclear inclusions or neurodegeneration. By 12 months of age, YAC72 mice have a selective degeneration of medium spiny neurons in the lateral striatum associated with the translocation of N-terminal htt fragments to the nucleus. Neurodegeneration can be present in the absence of macro- or microaggregates, clearly showing that aggregates are not essential to initiation of neuronal death. These mice demonstrate that initial neuronal cytoplasmic toxicity is followed by cleavage of htt, nuclear translocation of htt N-terminal fragments, and selective neurodegeneration.