Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / On t.p. "F̳u̳" is superscript. Includes bibliographical references (leaves 131-161). Also available in electronic version.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

To exit a non-proliferative state and enter cell division, metazoan cells require external signals to facilitate activation and metabolic reprogramming. As cell growth is required before cell division, cells redirect their metabolism for de novo synthesis of cell building blocks, including phospholipids for cell membrane construction. How cells coordinate initial signaling events with metabolism is unknown. Lineage-specific factors transmit activating signals via cell surface receptor-ligand interactions. Among these are PI3K/AKT, MAPK/ERK, and JAK/STAT, all of which have been described to contribute to metabolic regulation. In particular, the signal transducer and activator of transcription (STAT) is a transcription factor with broad roles in cell cycle progression and glucose metabolism. Previous data from our laboratory found that one STAT family member, STAT3, was one of the primary signaling pathways activated when transitioning out of a resting state. Inhibition of STAT3 was found to suppress the initiation of cell growth and citrate levels, a main intermediate for fatty acid synthesis, suggesting a connection to cell metabolism. This thesis investigates the role of STAT3 in the regulation of metabolism in cells transitioning from a resting state to a cell growth state. The first chapter of this thesis provides relevant background information on the metabolic and signaling pathways involved in a resting and cell growth state. It also provides data that supports an important role for STAT3 during initial cell growth. The second chapter demonstrates the importance of STAT3 in multiple cell types using a small molecule inhibitor of STAT3, STAT3 knockdown, and knockout experiments. I also establish a potential link between STAT3 and the metabolic enzyme citrate synthase (CS) for the synthesis of citrate. In the third chapter I show that STAT3 transcriptionally regulates CS through two binding sites, CS1 and CS2. Finally, I determine that CS is essential for initial cell growth and that exogenous citrate can rescue the loss in cell growth and proliferation observed in the CS and STAT3 knockdown cells. Together, these findings describe a novel mechanism for initial cell growth whereby signaling and metabolic events are tightly linked to regulate the transition from a resting state to a state of initial cell growth. These results may uncover new strategies to block the initiation of proliferation in human pathological conditions including tumor recurrence and autoimmunity. / Graduate

Thesis (Ph. D.)--University of Chicago, Committee on Immunology, June 2001. / Includes bibliographical references. Also available on the Internet.

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

Ca2+ signaling is essential for a wide variety of cellular activities, ranging from short term activities, such as synaptic and muscle contraction, to long term processes, such as proliferation and differentiation. Store-operated Ca2+ entry (SOCE), an important Ca2+ influx pathway in non-excitable cells, well coordinates Ca2+ release from ER and Ca2+ influx through plasma membrane. STIM1 and Orai1, serving as ER Ca2+ sensor and pore forming subunit, respectively, are the two essential components of SOCE machinery. In addition to activate Orai1 channel, studies have shown that STIM1 regulates other plasma membrane Ca2+ channels and senses a variety of cellular stresses to regulate SOCE. Therefore, it is of great interests to investigate the mechanisms and physiological functions of STIM1 and Orai1 mediated SOCE. Here, we performed tandem affinity purification to identify STIM1 associated proteins in Hela cells stably expressing STIM1-His6-3×Flag. Four candidate proteins, including GRP78, HSP70, IQGAP1, and Actin, were identified by mass spectrometry analyses. Surprisingly, IQGAP1 failed to affect the activity of SOCE. Interestingly, GRP78 knockdown only affected the inactivation phase while exerted no effect on the activation phase of SOCE. In addition, GRP78 knockdown markedly induced cell apoptosis and dramatically increased the ER Ca2+ concentration. Moreover, GRP78 was involved in the regulation of SOCE by the ER stress. These data indicate that GRP78 is an important regulator of SOCE to prevent Ca2+ overload in cells. HSP70, however, significantly reduced the activity of SOCE by inhibiting STIM1 translocation to ER-PM junctions. Future studies will explore the mechanism of GRP78 and HSP70 in regulating SOCE by confocal and TIRF imaging. Embryonic stem (ES) cells proliferate unlimitedly and can differentiate into all fetal and adult cell types. This property endows ES cells to be the promising candidates in the therapy of neurodegenerative diseases. Thus, it is important to identify novel signaling molecules or events that could play a role in the neural commitment of ES cells. Accumulated evidences have documented the role of STIM1 and Orai1 mediated SOCE in neuronal activities. Yet, the role of SOCE in early neural development remains to be determined. Here we examined the role of STIM1 and Orai1 during neural differentiation of mouse ES cells. Both of STIM1 and Orai1 were expressed and functionally active in ES cells, and expressions of STIM1 and Orai1 were dynamically regulated during neural differentiation of mouse ES cells. STIM1 knockdown inhibited the differentiation of mouse ES cells into neural progenitors, neurons, and astrocytes. In addition, STIM1 knockdown caused severe cell death and markedly suppressed the proliferation of neural progenitors. Surprisingly, Orai1 knockdown had little effect on neural differentiation of mouse ES cells, but the neurons derived from Orai1 knockdown ES cells, like those from STIM1 knockdown cells, had defective SOCE. Taken together, our data indicate that STIM1 is required for neural differentiation of mouse ES cells independent of Orai1-mediated SOCE. / published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

APPL BAR-PH heterodimer and APPL2 BAR-PH homodimer The APPL (Adaptor protein containing PH domain, PTB domain and Leucine zipper) family are adaptor proteins with only two isoforms, APPL1 and APPL2. They bind to early endosomes with a small GTPase, Rab5, and mediate the interactions between various receptors and downstream signaling components, thus functioning in many signaling pathways evoked by adiponectin, insulin, FSH, EGF, and so on. However, evidences have shown APPL1 and APPL2 should perform some opposite functions, which cannot be simply explained by the functional differences attributed to their PTB domains. We hypothesize that the heterodimerization of APPL1 and APPL2’s BAR domains may account for their opposing functions. The crystal structure of APPL BAR-PH heterodimer was solved to resolution 2.8 Å. Its overall structure exhibits crescent shape with a larger curvature radius of 76 Å, compared to 55 Å of the APPL1 BAR-PH homodimer. And the crystal structure APPL2 BAR-PH homodimer was solve to resolution 3.3 Å. The overall structure of APPL2 BAR-PH homodimer is very similar to that of APPL BAR-PH heterodimer, but shows greater difference in curvature to the APPL1 BAR-PH homodimer structure. The concave side of APPL BAR-PH heterodimer and APPL2 BAR-PH homodimer all possess less positive charge than the APPL1 BAR-PH homodimer. Structural analysis reveals that leucine patches at the dimer interface may account for the formation of dimeric curve with certain curvature. Consequently, APPL2 BAR is able to enforce the curvature reduction to APPL1 BAR upon heterodimerization. In conclusion, the alterations of curvature and electrostasis are responsible for the modulation of endosome binding specificity and can elucidate the opposite roles of APPL1 and APPL2. LanCL2 LanCL2 is a member of Lanthionine synthetase component C-like family. In human, LanCL2 binds to lanthionine derivatives and glutathione, participating in keeping intracellular reducing state. By binding to absiscic acid (ABA), LanCL2 is indispensible for the ABA-stimulated adipogenesis, insulin release, glucose homeostasis, and inflammatory response. It is also implicated in anticancer drug resistance. All these functions underscore the importance of LanCL2 in the diseases like diabetes, inflammation, and cancer. The crystal structure of LanCL2 was solved to resolution 1.8 Å. The overall structure displays canonical double-layer α-barrel. The major differences from LanCL1 lay in the loops on the barrel top, which are implicated in various substrate bindings. A zinc-coordinating pocket was found among the loops, with conserved amino acid residues of distinct conformation. The electrostatic surface shows remarkable differences compared to that of LanCL1, suggesting that it may contribute to distinct substrate binding profile. Future implications APPL proteins and LanCL proteins are all involved in the regulation of metabolism, such as glucose uptake, fatty acid oxidation, and insulin secretion, and play roles in diseases like obesity and type 2 diabete. Structural and functional studies of these proteins can provide insights into the molecular mechanisms and clues for related therapeutic approaches. / published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

No description available.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Non-Latin script record Includes bibliographical references (leaves 125-151). Also available on the World Wide Web.