Cell surface proteins play a critical role in facilitating movement of immune cells throughout the body. One such protein is CD9 which is expressed in immune and parenchymal cells. CD9 is a member of the tetraspanin superfamily and is involved in regulating various cellular processes including cell motility, adhesion, apoptosis, and metastasis. Recent studies have shown that the isignaling molecule called interleukin-16 (IL-16) is a possible ligand to activate CD9. Understanding immune response pathways such as observed between IL-16 and CD9 will provide valuable information on factors that contribute to maintaining a healthy immune system. For this project, students will examine the intracellular signaling pathways mediated by IL-16 activation through the CD9 receptor in a lung epithelial cell line (A549). There is also the possibility of examining the role of IL-16 signaling through CD9 in mouse neurons.
Neuronal Interleukin-16 (NIL-16) is the neuronal-specific splice isoform of the interleukin-16 (IL16) gene. NIL-16 shows restricted expression to the hippocampus and cerebellum: brain regions involved in learning and memory. The NIL-16 splice variant shares identical C-terminal protein-coding sequence with pro-IL-16; the shorter, immune-specific splice isoform that is the pro-inflammatory precursor to the cytokine IL-16. The mutual amino acid sequence between pro-IL-16 and NIL-16 contains three PDZ protein interaction domains (PDZ-1, PDZ-2 and PDZ-2). In addition to serving as the precursor to IL-16, pro-IL-16 regulates immune cell proliferation through a PDZ-2 mediated-interaction with the chromatin-modifying protein HDAC3. HDAC3 plays a critical role in regulating normal brain development and in fundamental processes of learning and memory. We hypothesize that like pro-IL-16, a protein-protein interaction exists between NIL-16 and HDAC3 suggesting the possibility of a protein complex important in mediating cellular activities in neurons. To test this hypothesis, we will conduct pulldown assays with mouse cerebellar brain extract using fusion proteins coding for the PDZ-2 domain of NIL-16 and the PDZ-interacting motif of HDAC3. We were able to affinity purify both HDAC3 with the NIL-16. In addition, in both heterologous cells and cerebellar cell extract, we will conduct co-immunoprecipitation assays using antibodies against HDAC3 and NIL-16 and shows the existence of an in vivo protein complex. Finally, we will use immunofluorescence microscopy, to demonstrate overlapping distribution of NIL-16 and HDAC3 in cultured cerebellar granule neurons.
Regulation secretion of insulin is required for proper glucose homeostasis; however, the molecular mechanism of insulin granule exocytosis have not been fully elucidated. In pancreatic β-cells, glucose-induced insulin secretion is synergistically potentiated through an Epac2-Rim2-Piccolo signaling response mechanism. Both Piccolo and Rim2 were originally identified as active zone proteins in neurons and have been shown to regulate synaptic vesicle cycling and neurotransmitter signaling. A recent study showed that a number of active zone proteins including Rim2 and Piccolo are down-regulated in human pancreatic islet cells isolated from patients with type 2 diabetes (T2D). Understanding the role of Piccolo in regulated secretion of insulin may provide valuable insights into the causes of T2D. The C-terminal region of Piccolo contains a Ca2+-binding C2A domain. It is likely that Piccolo may regulate secretion from insulin granule vesicles by serving as a Ca2+-sensor. For this project, students will conduct genetic deletion studies as well as over-expression of Piccolo splice variants to examine the role of this protein in regulating insulin secretion from a model rat pancreatic cell line (INS-823) that secretes human insulin.
Senior Sem Form