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Subcellular localization of adenosine kinase in mammalian cells: The long isoform of AdK is localized in the nucleus

2009; Elsevier BV; Volume: 388; Issue: 1 Linguagem: Inglês

10.1016/j.bbrc.2009.07.106

1090-2104

Xianying A. Cui, Bhag Singh, Jaeok Park, Radhey S. Gupta,

Biochemical and Molecular Research

Two isoforms of adenosine kinase (AdK) have been identified in mammalian organisms with the long isoform (AdK-long) containing extra 20–21 amino acids at the N-terminus (NTS). The subcellular localizations of these isoforms are not known and they contain no identifiable targeting sequence. Immunofluorescence labeling of mammalian cells expressing either only AdK-long or both isoforms with AdK-specific antibody showed only nuclear labeling or both nucleus and cytoplasmic labeling, respectively. The AdK-long and -short isoforms fused at the C-terminus with c-myc epitope also localized in the nucleus and cytoplasm, respectively. Fusion of the AdK-long NTS to green fluorescent protein also resulted in its nuclear localization. AdK-long NTS contains a cluster of conserved amino acids (PKPKKLKVE). Replacement of KK in this sequence with either AA or AD abolished its nuclear localization capability, indicating that this cluster likely serves as a nuclear localization signal. AdK in nucleus is likely required for sustaining methylation reactions.