Areas of Interest
My current research focus concerns the study of a gene
discovered in my lab which we term CHERP, i.e., Calcium
Homeostasis Endoplasmic Reticulum Protein. The cDNA for this
protein was cloned and sequenced from an HEL cell cDNA
expression library using monoclonal antibody to a human platelet
ER membrane constituent. Using FISH, the gene was localized to
chromosome 19 p13.1. An adenoviral vector was constructed that
permitted regulated expression of nearly full length CHERP
protein and a subsequent severe impairment of the ability of the
cells to mobilize Ca2+ when appropriately stimulated.
Immunofluorescence microscopy revealed that CHERP was
co-localized with the two intracellular Ca2+ channels that are
present in the ER/SR of cells, i.e. the InsP3-receptor and the
ryanodine receptor. The cells we studied were human neoplastic
cell lines, and their rapid rates of proliferation were sharply
reduced by depletion of CHERP. Furthermore, in Jurkat T-cells
the depletion of CHERP impaired the Ca2+- dependent nuclear
translocation of the key transcription factor NFAT which is
important for T-cell proliferation and differentiation. Current
studies are focused on the effects of CHERP knockdown on the
functional properties of cultured cardiac muscle cells and
neuroblastoma cells. Since our first discovery, several groups
have found the same protein in human tissues and in rodents by
cloning or by computer analysis of the genomes. Protein
sequences with varying degrees of sequence homology to CHERP
have been identified in the genomes of C. elegans, Drosophila
and zebra fish. The amino acid sequence of human CHERP is
unique, although it contains several putative domains found in
other proteins that function in interactions with RNA and RNA
polymerase II. This has led to proposal of an alternative name,
SCAF6, i.e., spiceosome associated factor 6. It was proposed
that SCAF6 has a domain that binds to RNA pol II, and could be
involved in mRNA splicing and synthesis. However, we do not find
localization of CHERP in the nuclei of cells where RNA pol II is
predominantly found. Current studies in our lab using siRNA and
morpholino oligos to knockdown CHERP are in progress in order to
determine the functional roles for this protein in cardiac
muscle.
Selected Publications
O'Rourke FA, LaPlante JM, Feinstein MB. 2003. Antisense-mediated
loss of calcium homoeostasis endoplasmic reticulum protein (CHERP;
ERPROT213-21) impairs Ca2+ mobilization, nuclear factor of
activated T-cells (NFAT) activation and cell proliferation in
Jurkat T-lymphocytes. Biochem J. Jul 1;373(Pt 1):133-43.
Laplante JM, O'Rourke F, Lu X, Fein A, Olsen A, Feinstein MB.
2000. Cloning of human Ca2+ homoeostasis endoplasmic reticulum
protein (CHERP): regulated expression of antisense cDNA depletes
CHERP, inhibits intracellular Ca2+ mobilization and decreases
cell proliferation. Biochem J. May 15;348 Pt 1:189-99.
Lu X, Fein A, Feinstein MB, O'Rourke FA. 1999. Antisense
knock out of the inositol 1,3,4,5-tetrakisphosphate receptor
GAP1(IP4BP) in the human erythroleukemia cell line leads to the
appearance of intermediate conductance K(Ca) channels that
hyperpolarize the membrane and enhance calcium influx. J Gen
Physiol. Jan;113(1):81-96.
Armando P. Signore, Flavia O'Rourke, Xinghua Lu, Maurice B.
Feinstein, andHermes H. Yeh (1999) Immunohistochemical
localization of the InsP4 receptor GTP-ase activating protein
GAP1IP4BP in the rat brain. J. NeuroscienceResearch 55: 321-328. |
