Unique Reliance Research Articles

Carnitine transporter CT2 (SLC22A16) is over-expressed in acute myeloid leukemia (AML) and target knockdown reduces growth and viability of AML cells.

AML (acute myeloid leukemia) cells have a unique reliance on mitochondrial metabolism and fatty acid oxidation (FAO). Thus, blocking FAO is a potential therapeutic strategy to target these malignant cells. In the current study, we assessed plasma membrane carnitine transporters as novel therapeutic targets for AML. We examined the expression of the known plasma membrane carnitine transporters, OCTN1, OCTN2, and CT2 in AML cell lines and primary AML samples and compared expression to normal hematopoietic cells. Of the three carnitine transporters, CT2 demonstrated the greatest differential expression between AML and normal cells. Using shRNA, we knocked down CT2 and demonstrated that target knockdown impaired the function of the transporter. In addition, knockdown of CT2 reduced the growth and viability of AML cells with high expression of CT2 (OCI-AML2 and HL60), but not low expression. CT2 knockdown reduced basal oxygen consumption without a concomitant increase in glycolysis. Thus, CT2 may be a novel target for a subset of AML.

Genetic ablation of N-linked glycosylation reveals two key folding pathways for R345W fibulin-3, a secreted protein associated with retinal degeneration.

An R345W mutation in the N-glycoprotein, fibulin-3 (F3), results in inefficient F3 folding/secretion and higher intracellular F3 levels. Inheritance of this mutation causes the retinal dystrophy malattia leventinese. N-Linked glycosylation is a common cotranslational protein modification that can regulate protein folding efficiency and energetics. Therefore, we explored how N-glycosylation alters the protein homeostasis or proteostasis of wild-type (WT) and R345W F3 in ARPE-19 cells. Enzymatic and lectin binding assays confirmed that WT and R345W F3 are both primarily N-glycosylated at Asn249. Tunicamycin treatment selectively reduced R345W F3 secretion by 87% (vs. WT F3). Genetic elimination of F3 N-glycosylation (via an N249Q mutation) caused R345W F3 to aggregate intracellularly and adopt an altered secreted conformation. The endoplasmic reticulum (ER) chaperones GRP78 (glucose-regulated protein 78) and GRP94 (glucose-regulated protein 94), and the ER lectins calnexin and calreticulin were identified as F3 binding partners by immunoprecipitation. Significantly more N249Q and N249Q/R345W F3 interacted with GRP94, while substantially less N249Q and N249Q/R345W interacted with the ER lectins than their N-glycosylated counterparts. Inhibition of GRP94 ATPase activity reduced only N249Q/R345W F3 secretion (by 62%), demonstrating this variant's unique reliance on GRP94 for secretion. These observations suggest that R345W F3, but not WT F3, requires N-glycosylation to acquire a stable, native-like structure.

Pancreatic cancers depend on a non-canonical glutamine metabolism pathway

Cancer cells exhibit metabolic dependencies that distinguish them from their normal counterparts. Among these addictions is an increased utilization of the amino acid glutamine (Gln) to fuel anabolic processes. Recently, we reported the identification of a non-canonical pathway of Gln utilization in human pancreatic cancer cells that is required for tumor growth. While most cells utilize glutamate dehydrogenase (GLUD1) to convert Gln-derived glutamate (Glu) into a-ketoglutarate (aKG) in the mitochondria to fuel the tricarboxylic acid cycle, pancreatic cancer cells rely on a distinct pathway that integrates the mitochondrial and cytosolic aspartate aminotransferases GOT2 and GOT1. By generating aKG from Glu (in conjunction with the conversion of oxaloacetate into aspartate), GOT2 fuels anaplerosis in place of GLUD1. The Asp created is released into the cytosol and acted on by GOT1. This is subsequently used through as eries of reactions to yield cytosolic NADPH from malic enzyme. Importantly, we have demonstrated that pancreatic cancers are strongly dependent on this series of reactions to maintain redox homeostasis which enables proliferation. Herein, we detail the subcellular compartmentalization and consequences of the aforementioned reactions on pancreatic cancer metabolism. We have also investigated the essentiality of this pathway in other contexts and find that pancreatic cancers have a uniform and unique reliance on this pathway, which may provide novel therapeutic approaches to treat these refractory tumors.

Built to bite: cranial design and function in the wrinkle‐faced bat

AbstractOne of the major goals of evolutionary biology is to explain phenotypic diversity and understand the limits imposed by those phenotypes. The cranial morphology of the wrinkle‐faced bat Centurio senex (Family Phyllostomidae) is bizarre and enigmatic. Its extremely short and wide skull consistently emerges as an outlier in morphological studies and many researchers have speculated about its function. Here, we investigate the hypothesis that the unique skull morphology of Centurio is associated with the ability to generate high bite forces and/or high bite forces at wide gapes. We accomplish this by comparing bite force data gathered in the field and estimates of gape limitations gathered from museum specimens. We also examine the possibility that Centurio uses unique feeding behaviors that may impose unique loading regimes on the facial skeleton. We found that relative to head size, Centurio generates the strongest bites known for any fruit‐eating phyllostomid bat, but that its ability to generate high bite forces at wide gape angles is likely limited. We also propose that its exceptionally strong bite indicates the ability to consume hard food items when other resources are limited, and that these ‘resource bottlenecks’ may have imposed strong selective pressure on its skull morphology. Behavioral data indicate that Centurio exhibits a unique reliance on unilateral biting (loading) during feeding. Based on data summarizing bite force, estimates of gape ability and feeding behavior, we suggest that Centurio's exceptionally short and wide skull reflects adaptations for high bite forces and repeated unilateral loading of the facial skeleton during feeding.

Identification and Stage-specific Association with the Translational Apparatus of TbZFP3, a CCCH Protein That Promotes Trypanosome Life-cycle Development

The post-transcriptional control of gene expression is becoming increasingly important in the understanding of regulated events in eukaryotic cells. The parasitic kinetoplastids have a unique reliance on such processes, because their genome is organized into polycistronic transcription units in which adjacent genes are not coordinately regulated. Indeed, the number of RNA-binding proteins predicted to be encoded in the genome of kinetoplastids is unusually large, invoking the presence of unique RNA regulators dedicated to gene expression in these evolutionarily ancient organisms. Here, we report that a small CCCH zinc finger protein, TbZFP3, enhances development between life-cycle stages in Trypanosoma brucei. Moreover, we demonstrate that this protein interacts both with the translational machinery and with other small CCCH proteins previously implicated in trypanosome developmental control. Antibodies to this protein also co-immunoprecipitate EP procyclin mRNA and encode the major surface antigen of insect forms of T. brucei. Strikingly, although TbZFP3 is constitutively expressed, it exhibits developmentally regulated association with polyribosomes, and mutational analysis demonstrates that this association is essential for the expression of phenotype. TbZFP3 is therefore a novel regulator of developmental events in kinetoplastids that acts at the level of the post-transcriptional control of gene expression.

Detecting remotely related proteins by their interactions and sequence similarity

The function of an uncharacterized protein is usually inferred either from its homology to, or its interactions with, characterized proteins. Here, we use both sequence similarity and protein interactions to identify relationships between remotely related protein sequences. We rely on the fact that homologous sequences share similar interactions, and, therefore, the set of interacting partners of the partners of a given protein is enriched by its homologs. The approach was bench-marked by assigning the fold and functional family to test sequences of known structure. Specifically, we relied on 1,434 proteins with known folds, as defined in the Structural Classification of Proteins (SCOP) database, and with known interacting partners, as defined in the Database of Interacting Proteins (DIP). For this subset, the specificity of fold assignment was increased from 54% for position-specific iterative BLAST to 75% for our approach, with a concomitant increase in sensitivity for a few percentage points. Similarly, the specificity of family assignment at the e-value threshold of 10(-8) was increased from 70% to 87%. The proposed method would be a useful tool for large-scale automated discovery of remote relationships between protein sequences, given its unique reliance on sequence similarity and protein-protein interactions.

Discipline Identification in Chemistry and Physics

The ArgumentDuring the nineteenth century, physicists and chemists, using different linguistic modes of expression, sought to describe the world for different purposes; thus, both disciplines gradually were nudged toward demarcation and self-image identification. In the course of doing so the rich complexity of the empire of chemistry was born. The essential challenge was closely connected with analysis, synthesis, and chemical process: learning the art ofwatchingsubstances change andmakingsubstances change. Pursued in theory-poor and phenomenology-rich contexts chemistry nevertheless made itself intellectually, professionally, societally, and industrially creditable and attractive. The developing links between physics and chemistry are examined in this paper from the perspective of the discipline of chemistry more specifically than from the side of physics. Chemists came to believe that essentially physics was no more than mechanics. All else belonged to the domain of chemistry.Not before the last decades of the century were firm collaborative links and genuine reciprocity fostered between physics and chemistry, and then primarily on account of the common utility of scientific research tools. At a more fundamental level physics and chemistry, in contradistinction to all the other natural sciences, experienced partial overlap and convergence because of unique mutual reliance on the construction of systems each according to its own theoretical conceptions. Still amalgamation was unthinkable. Eventually physical chemistry was loosened from chemistry in the same way that, somewhat later, chemical physics was emancipated from physics. The intrinsic messiness of chemistry, one might suggest, tends more readily to foster Bohr's opinion that “there is no rock bottom to the study of nature,” rather than Einstein's view that “we can realistically, ultimately, put it all together.”

Verbal vulnerability of perceptual expertise.

Three experiments explored the role of perceptual expertise in mediating the finding (termed verbal overshadowing) that describing a face can impair later recognition. In Experiment 1, verbalization impaired White participants' recognition of White faces (expert domain) but not African American faces (novice domain). In Experiment 2, judges attempted to identify targets on the basis of the verbal descriptions generated in Experiment 1. Experiment 2 revealed a significant relationship between verbalization participants' recognition performance and yoked judges' identification performance for other-race but not own-race faces, suggesting that other-race recognition may involve a unique reliance on "verbalizable" information. In Experiment 3, the interaction between verbalization and race of face was replicated with upright faces but was attenuated with inverted recognition arrays (a manipulation that reduces the influence of configural information). Collectively, these findings suggest that verbalization may disrupt the nonreportable configural processes associated with recognizing stimuli with which one is an expert.

Design Forces for Drift and Damage Control: A Second Look at the Substitute Structure Approach

This paper explores the development of a method that is useful for design of reinforced concrete (RC) frame structures to resist earthquakes. The substitute structure method, originally proposed in the 1970s, makes an analogy between viscously damped linear and hysteretic response for the purpose of estimating maximum displacement. The evolution of the method is retraced in order to emphasize its unique reliance on experimental results, which are needed to establish rules for assignment of substitute linear properties. Recent dynamic test results are used to extend significantly the calibration of the method, which furnishes design loads on the basis of drift and damage control.

Controlling AIDS in Cuba. The logic of quarantine.

Unlike any other nation, Cuba has embarked on a program to control the acquired immunodeficiency syndrome (AIDS) that is designed to limit the spread of infection with the human immunodeficiency virus (HIV) by invoking the compulsory elements of the public health tradition. Widespread screening for HIV infection began in Cuba three years ago, and persons identified as infected have been sent to a sanatorium located in a Havana suburb. This unique reliance on a modified quarantine extends to all HIV-infected persons. A recent visit to Cuba as guests of the Ministry of Health permitted us to talk with Cuban officials . . .