hIan5: the human ortholog to the rat Ian4/Iddm1/lyp is a new member of the Ian family that is overexpressed in B-cell lymphoid malignancies

Genes Immun. 2004 Mar;5(2):109-16. doi: 10.1038/sj.gene.6364044.


The family of immune associated nucleotide binding proteins (Ian) is a distinct family of GTP-binding proteins conserved in plants, mice, rats and humans that are associated with immune functions, suggesting involvement in conserved defense mechanisms. Recently, the rat Ian4 (rIan4) was cloned and it appears to be identical to the gene Iddm1/lyp responsible for severe lymphopenia and the development of insulin-dependent diabetes in the BB-DP rat. Here we describe the characterization of a new human member of the Ian family: hIan5. hIan5 is highly homologous to rIan4, has a predicted molecular weight of 35 kDa and contains distinct G motifs of GTP-binding proteins (G-1 to G-4) in the N-terminus. Human Ian5 is anchored to the mitochondria by the hydrophobic COOH-terminal domain. Human Ian5 is highly expressed in lymph node and spleen. Different blood fractions show high hIan5 expression in CD4- and CD8-positive T cells and monocytes, but not in B lymphocytes. In contrast, in B-CLL (chronic lymphocytic leukemia) and mantle cell lymphoma samples, hIan5 mRNA was upregulated. The current data underline the role of hIan5 in T-lymphocyte development and function, and for the first time suggest that upregulation of Ian proteins is associated with B-cell malignancy, possibly by inhibiting apoptosis.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Blotting, Western
  • Cell Fractionation
  • Chromosomes, Human, Pair 7 / genetics*
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / metabolism*
  • Humans
  • Leukemia, Lymphocytic, Chronic, B-Cell / metabolism*
  • Lymph Nodes / metabolism
  • Microscopy, Fluorescence
  • Mitochondria / metabolism*
  • Molecular Sequence Data
  • Multigene Family / genetics
  • Plasmids / genetics
  • RNA / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Alignment
  • Sequence Analysis, DNA
  • Spleen / metabolism
  • T-Lymphocytes / metabolism
  • Transfection
  • Tumor Cells, Cultured


  • GIMAP5 protein, human
  • RNA
  • GTP-Binding Proteins