Small Proline Rich Protein-2 Expression and Regulation in the Caco-2 model of Intestinal Epithelial Differentiation along the Crypt-Villus Axis

Small proline-rich protein-2 (SPRR2) functions as a determinant of flexibility and permeability in the mature cornified envelope of the skin. SPRR2 is strongly upregulated by the commensal flora and may mediate signaling to differentiated epithelia of the small intestine and colon. Yet, SPRR2 function in the GI tract is largely unexplored. Using the Caco-2 model of intestinal epithelial differentiation along the crypt-villus axis, we hypothesized that SPRR2 would be preferentially expressed in post-confluent differentiated Caco-2 cells and examined SPRR2 regulation by the protein kinase A pathway (PKA) and short chain fatty acids (SCFAs). Differentiation-dependent SPRR2 expression was examined in cytoskeletal-, membrane-, and nuclear-enriched fractions by immunoblotting and confocal immunofluorescence. We studied the effect of SCFAs, known inducers of differentiation, on SPRR2 expression in pre-confluent undifferentiated Caco-2 cells and explored potential mechanisms involved in this induction using MAP kinase inhibitors. SPRR2 expression was also compared between HIEC crypt cells and 16 to 20 week primary fetal villus cells as well as in different segments in mouse small intestine and colon. We determined if SPRR2 is increased by gram negative bacteria such as S. typhimurium. SPRR2 expression increased in a differentiation-dependent manner in Caco-2 cells and was present in human fetal epithelial villus cells but absent in HIEC crypt cells. Differentiation-induced SPRR2 was down-regulated by 8-Br-cAMP as well as by forskolin/IBMX co-treatment. SPRR2 was predominantly cytoplasmic and did not accumulate in Triton X-100-insoluble cytoskeletal fractions. SPRR2 was present in the membrane- and nuclear-enriched fractions and demonstrated co-localization with F-actin at the apical actin ring. No induction was seen with the specific HDAC inhibitor trichostatin A, while SCFAs and the HDAC inhibitor SBHA all induced SPRR2. SCFA responses were inhibited by MAP kinase inhibitors SB203580 and U0126, thus suggesting that the SCFA effect may be mediated by orphan G-protein receptors GPR41 and GPR43. S. typhimurium induced SPRR2 in undifferentiated cells. We conclude that SPRR2 protein expression is associated with differentiated epithelia and is regulated by PKA signaling and by by-products of the bowel flora. This is the first report to establish an in vitro model to study the physiology and regulation of SPRR2.

CYSTATIN RELATED EPIDIDYMAL SPERMATOGENIC PROTEIN RESIDES IN THE OUTER DENSE FIBRES AND LIKELY TRANSIENTLY ASSOCIATES WITH THE SURFACE OF EPIDIDYMAL MOUSE SPERMATOZOA

Cystatin Related Epididymal Spermatogenic protein (CRES) is expressed in both the testis and epididymis and found associated with spermatozoa. It appears as non-glycosylated (14 and 12 kDa) and glycosylated isoforms (19 and 17 kDa). The role of CRES is enigmatic and dependent on localization of its isoforms, which is the objective of this study. The initial approach was to investigate testicular and epididymal origins of these isoforms by immunohistochemistry and immunogold cytochemistry. To further pinpoint CRES localization we then selectively extracted and fractionated epididymal spermatozoa in order to find by immunoblotting which sperm fractions contained CRES isoforms. Immunohistochemical analysis of mouse spermatogenesis showed that CRES was expressed in the tail cytoplasm of elongating spermatids from step 9-16, with a pattern reminiscent of outer dense fibre (ODF) proteins. Ultrastructural immunocytochemistry revealed that the immunogold label was concentrated over growing ODFs and mitochondrial sheath in the testes which persisted in spermatozoa through the epididymis. Sequential extractions of isolated sperm tails with Triton X-100-dithiothreitol (DTT) to remove the mitochondrial sheath, whose extract contained an unrelated 66 kDa immunoreactive band, followed by either sodium dodecyl sulfate (SDS)-DTT or urea-DTT to solubilise accessory fibres of the tail revealed a 14 kDa immunoreactive band associated with the ODF. In addition, Western blots revealed glycosylated and non-glycosylated CRES isoforms in nonyl phenoxylpolyethoxylethanol (NP40) extracts of the caput, but not cauda, sperm. Immunohistochemical analysis of the caput and cauda epithelium showed that CRES is secreted by the Golgi apparatus of the ii initial segment, fills the proximal caput lumen, and disappears by mid caput. Western blots of caput and cauda tissue and luminal fluid revealed 14 and 19 kDa immunoreactive bands in caput tissues and luminal fluid, but not in the cauda. This study concludes that there are two origins of CRES, one arising in the testis and the other in the epididymis. Testicular CRES is ionically and covalently associated with the ODF while epididymal CRES is detergent soluble and is most likely associated temporarily with the surface of caput epididymal sperm.

IMPACT OF RNA VIRUSES ON THE REGULATION OF IL-23 IN MOUSE AND HUMAN MODELS OF INFECTION.

Interluekin-23 (IL-23) is a pro-inflammatory cytokine critical to the regulation of innate and adaptive immune responses. The main role for this cytokine is in the proliferation and differentiation of the IL-17 producing CD4 T helper cell, Th17. Virus infection deregulates IL-23 expression and function, but little is known about the mechanism behind this phenomena. Here, I demonstrate a reduction of Toll like receptor (TLR) ligand-induced IL-23 expression in lymphocytic choriomeningitis virus (LCMV)-infected bone marrow-derived dendritic cells (BMDCs), indicating that a function of these cells is disrupted during virus infection. I propose a mechanism of TLR ligand-induced IL-23 expression inhibition upon LCMV infection via the deactivation of p38, AP-1, and NF-κB. Further analysis revealed a direct relationship between LCMV infection with the IL-10 and SOCS3 expression. To understand IL-23 function, I characterized IL-23-induced JAK/STAT signalling pathway and IL-23 receptor expression on human CD4 T cells. My results demonstrate that IL-23 induces activation of p-JAK2, p-Tyk2, p-STAT1, p-STAT3, and p-STAT4 in CD4 T cells. For the first time I show that IL-23 alone induces the expression of its own receptor components, IL-12Rβ1 and IL-23Rα, in CD4 T cells. Blocking JAK2, STAT1, and STAT3 activation with specific inhibitors detrimentally effected expression of IL-23 receptor demonstrating that activation of JAK/STAT signalling is important for IL-23 receptor expression. I also addressed the effect of viral infection on IL-23 function and receptor expression in CD4 T cells using cells isolated from HIV positive individuals. These studies were based on earlier reports that the expression of IL-23 and the IL-23 receptor are impaired during HIV infection. I demonstrate that the phosphorylation of JAK2, STAT1, and STAT3 induced by IL-23, as well as IL-23 receptor expression are deregulated in CD4 T cells isolated from HIV positive individuals. This study has furthered the understanding of how the expression and function of IL-23 is regulated during viral infections.

FES KINASE SIGNALING PROMOTES MAST CELL RECRUITMENT TO TUMOURS

FES protein-tyrosine kinase (PTK) activation downstream of the KIT receptor in mast cells (MC) promotes cell polarization and migration towards the KIT ligand Stem cell factor (SCF). A variety of tumours secrete SCF to promote MC recruitment and release of mediators that enhance tumour vascularization and growth. This study investigates whether FES promotes MC migration via regulation of microtubules (MTs), and if FES is required for MC recruitment to the tumour microenvironment. MT binding assays showed that FES has at least two MT binding sites, which likely contribute to the partial co-localization of FES with MTs in polarized bone marrow-derived mast cells (BMMCs). Live cell imaging revealed a significant defect in chemotaxis of FES-deficient BMMCs towards SCF embedded within an agarose drop, which correlated with less MT organization compared to control cells. To extend these results to a tumour model, mouse mammary carcinoma AC2M2 cells were engrafted under the skin and into the mammary fat pads of immune compromised control (nu/nu) or FES-deficient (nu/nu:fes-/-) mice. A drastic reduction in tumour-associated MCs was observed in FES-deficient mice compared to control in both mammary and skin tissue sections. This correlated with a trend towards reduced tumour volumes in FES-deficient mice. These results implicate FES signaling downstream of KIT, in promoting MT reorganization during cell polarization and for chemotaxis of MCs towards tumour-derived SCF. Thus, FES is a potential therapeutic target to limit recruitment of stromal mast cells or macrophages to solid tumours that enhance tumour progression.

Mouse Uterine Natural Killer Cell Functions During Early Pregnancy

Early pregnancy is characterized by complex interactions between blood vessels, leukocytes, and conceptus-derived trophoblasts within the gestational uterus. Uterine Natural Killer (uNK) cells become the most abundant leukocyte during decidualization and produce a wide array of angiogenic factors, yet little is known regarding their early pregnancy functions. To characterize the role(s) of uNK cells, whole mount in situ immunohistochemistry of live early implant sites was performed. A timecourse examination of murine early pregnancy (virgin, and gd4.5-9.5) implantation sites was performed. Comparison of Gd6.5, 8.5 and 9.5 implant sites from BALB/c+/+ controls (BALB/c) and BALB/c-Rag2-/-Il2rg-/- (alymphoid) identified anomalies that result from the absence of lymphocytes. In alymphoid decidua basalis, mesometrial angiogenesis was widespread but pruning of nascent vessels within alymphoid decidua basalis was deficient. As early gestation progressed, vessels of alymphoid decidua basalis showed no evidence for remodeling. Alymphoid implantation sites showed ~24h delay in uterine lumen closure and embryonic development. To determine if uNK cells would normalize the anomalies observed in alymphoid implantation sites, adoptive cell transfer of NK+ B- T- marrow to alymphoid mice was performed. All of the above anomalies were reversed by adoptive transfer of NK+B-T- marrow. My results suggest that uNK cells support vascular growth and development which ensures the decidua can support the growing conceptus early in pregnancy prior to formation and function of the placenta. Human decidual NK cells may fill similar roles and be important targets for strategies designed to correct intra-uterine growth restriction.