Protein kinases constitute a large superfamily of enzymes with key regulatory functions in nearly all signal transmission processes of eukaryotic cells . FER is found in the cytoplasm and in the nucleus, where it was associated with the chromatin fraction. Its ubiquitous expression and its subcellular location indicate that it may be involved in key regulatory processes . The group IV cytoplasmic protein-tyrosine kinase Fer has been linked to cellular signaling responses to many different stimuli, including growth factors and cytokines. Data suggest a biological role for Fer in regulation of leukocyte recruitment during the innate immune response .