Journal of Cellular Biochemistry 86:509–519 (2002) Altered Expression and Localization of N-Myristoyltransferase in Experimentally Induced Rat Model of Ischemia-Reperfusion Raju V.S. Rajala, 1 Rakesh Kakkar, 1 Rani Kanthan, 1 Jasim M. Radhi, 1 Xintao Wang, 2 Rui Wang, 2 Raju S.S. Datla, 3 and Rajendra K. Sharma 1 * 1 Department of Pathology and Saskatoon Cancer Centre, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 4H4, Canada 2 Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 4H4, Canada 3 Plant Biotechnology Institute, National Research Council, Saskatoon, Saskatchewan, S7N 0W9, Canada Abstract N-myristoyltransferase (NMT) catalyzes the attachment of myristate onto the amino-terminal glycine residue of select polypeptides. In the present study, we investigated the expression and activity of NMT in rat heart after ischemia and reperfusion. Western blot analysis of rat heart samples indicated a prominent immunoreactive band of 66 kDa probed with human NMT antibody. Both the expression and activity of NMT were increased by ischemia- reperfusion. Immunohistochemical studies showed cytosolic localization of NMT in normal rat heart and predominant nuclear localization after ischemia followed by reperfusion. The pre-ischemic perfusion and post-ischemic reperfusion of hearts with a cell-permeable calpain inhibitor (N-Ac-Leu-Leu-methioninal) suppressed the increase in calpain expression and reversed the localization of NMT from nucleus to cytoplasm. This is the first study demonstrating the expression and alteration of NMT localization in cardiac ischemia and pertaining to a possible role of co-translational modification of proteins in cardiac functions and injury. J. Cell. Biochem. 86: 509–519, 2002. ß 2002 Wiley-Liss, Inc. Key words: N-myristoyltransferase; c-Src; tyrosine kinase; ischemic heart; calpain Intracellular proteolysis by the calpains, membersoftheCa 2þ activatedcysteine protease family, is an ubiquitous yet a poorly understood process. These proteases are implicated in an array of cellular and pathological processes, including long-term potentiation, synaptic remodeling, protein kinase C-mediated and steroid receptor activation, ischemic cellular injury, and apoptosis [Caroall and Demartino, 1991; Saido et al., 1994; Kawasaki and Kawa- shima, 1996; Stabach et al., 1997]. There are at least two types of calpains (m- and m-calpains) which require a micromolar and a millimolar concentration of Ca 2þ for activation, respec- tively. The calpain activity is physiologically regulated by an endogenous calpain specific inhibitor, calpastatin [Murachi, 1997]. Cal- pains hydrolyze various endogenous proteins [Billger et al., 1988; David et al., 1993] including calmodulin-binding proteins [Kosaki et al., 1983; Wang et al., 1989; Barnes and Gomes, 1995], and components of receptor signaling pathways [Inoue et al., 1977; Magnuson et al., 1993]. Additionally, various transcription fac- tors, including API (c-Fos/c-Jun), AP 2, Pit-1, Oct 1, CP 1a and b, c-Myc, ATF/CREB and AP 3, have been found to be cleaved by m-calpain to produce specific partial digestion products [Hirai et al., 1991; Watt and Molloy, 1993]. N-myristoyltransferase (NMT) catalyzes the co-translational transfer of myristate from ß 2002 Wiley-Liss, Inc. Raju V.S. Rajala’s present address is Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104. Rakesh Kakkar’s present address is Wyeth Lederlee Vaccines, Pearl River, New York. Jasim M. Radhi’s present address is McMaster University Medical Center Site, Hamilton, Ontario L8N3ZS, Canada. *Correspondence to: Rajendra K. Sharma, PhD, Depart- ment of Pathology and Saskatoon Cancer Centre, College of Medicine, University of Saskatchewan, Saskatoon, Sas- katchewan, Canada S7N 4H4. E-mail: rsharma@scf.sk.ca Received 17 May 2002; Accepted 21 May 2002 DOI 10.1002/jcb.10248