|Cheng, Ning-Hui - BAYLOR COLLEGE MED|
|Rees, Ian - BAYLOR COLLEGE MED|
Submitted to: Plant Biology
Publication Type: Abstract Only
Publication Acceptance Date: June 11, 2004
Publication Date: July 24, 2004
Citation: Cheng, N-H., Rees, I. 2004. Regulation of calcium transporters: The role of a nuclear-localized CAX-interacting protein, CXIP4 [abstract]. Plant Biology, Session 36: Membrane Transport, July 24-28, 2004, Lake Buena Vista, Florida. A175, p. 73. Technical Abstract: Regulation of calcium transporters is essential for modulating the Ca(2+) signaling and/or Ca(2+) homeostasis that are involved in the growth and adaptation of all organisms. The Arabidopsis H(+) /Ca(2+) antiporters, CAX1 and CAX1-like transporters, are autoinhibited and unable to suppress the hypersensitivity of yeast vacuolar Ca(2+) transporter mutants when heterologously expressed in yeast cell. Using a yeast functional screen, we identified several CAX interacting proteins (1-5) that activated full-length CAX1, but not full-length CAX2, CAX3 or CAX4. One of these, "CXIP4", encodes a novel plant protein with no bacterial, fungal, animal and mammalian homologs. "CXIP4" is highly expressed in all tissues of Arabidopsis. Expression of full-length CXIP4-GFP fusion in yeast and plant cells suggests that CXIP4 is predominately targeted to the nucleus. Using a yeast growth assay, we also demonstrated that CXIP4 activated a chimeric CAX construct that contained specific portions of the N-terminus of CAX1. CXIP4 has a unique structural feather, such as a Zn knuckle (CX2CX4HX4C motif) at the N-terminus and the multiple putative nuclear localized signal (NLS) motifs at its C-terminal region. Further investigation of the role of CXIP4 in regulating CAX-mediated Ca(2+) transport will be presented in the meeting. A potential link between nuclear-localized signal molecule and Ca(2+) signaling will also be discussed.