Project 1: Program in Cell Signaling

Our laboratory is studying cellular differentiation and the way this process is regulated by signal transduction.

The main focus is on a cytoplasmic protein-tyrosine kinase (PTK) designated Bruton’s tyrosine kinase, BTK. BTK belongs to the second largest family of mammalian PTKs, the TEC family (Smith et al., 2001) comprising BTK, BMX (ETK), ITK, TEC and TXK (RLK). BTK is affected in the disease named X-linked agammaglobulinemia (XLA), and was identified as a result of positional cloning (Vetrie et al., 1993). BTK was found to shuttle between the cytoplasm and the nucleus (Mohamed et al., 2000). BTK activates NF-kB signaling and is also regulated by this pathway through its own promoter (Yu et al. 2008).

One approach to understand the signaling process is to investigate structure-function relationships (Hansson et al., 1998 Fig. 1; Márquez et al., 2003). Main activities include cell biology, biochemistry, proteomics, imaging, expression profiling, and siRNA technology. In expression profiling studies of the ITK kinase, a unique transcriptome was identified, including the transcription factor PLZF (Blomberg et al., 2009; Raberger et al. 2008). These studies also include research in Drosophila (Hamada-Kawaguchi et al., 2014).

Using proteomics approaches, we have recently identified ankyrin repeat domain protein 54 (ANK54) and 14-3-3z as partners, which regulate BTK nucleo-cytoplasmic shuttling and degradation (Gustafsson et al. 2012, Mohammad et al. 2013). We are currently also studying other proteins, which show functional interaction with BTK, such as AKT.

Recently the translocation-based fusion-protein ITK-SYK causing lymphomas in humans has been investigated (Hussain et al., 2009 and 2013, Fig. 3). Studies related to BTK inhibitors, especially ibrutinib, are also ongoing with a focus on leukemia and lymphoma treatment.

We are also developing new treatment modalities for XLA based on splice-correcting oligonucleotides. Here we have generated humanized, transgenic mice lacking mouse BTK but carrying a splicing-deficient human BTK mutant. We have successfully corrected BTK pre-mRNA in B cells from these mice and restored BTK function in vitro (Bestas et al. manuscript).

Illustration of Fig. 1. A. Modified version of the NMR solution structure of the BTK-SH3 domain as determined by Hansson et al. Biochemistry. 1998 Mar 3;37(9):2912-24
Fig. 1. A. Modified version of the NMR solution structure of the BTK-SH3 domain as determined by Hansson et al. Biochemistry. 1998 Mar 3;37(9):2912-24. Photo: N/A
Illustration of Fig. 1. B. The structure of the pleckstrin homology (PH) domain and the BTK motif in Mohamed et al. Immunol Rev. 228(1):58-73, 2009.
Fig. 1. B. The structure of the pleckstrin homology (PH) domain and the BTK motif in Mohamed et al. Immunol Rev. 228(1):58-73, 2009. Photo: N/A
Illustration of Fig. 2. ANK54 is an ankyrin repeat, nucleocytoplasmic protein, colocalizing with BTK in the cytoplasm, inner membrane, and perinuclear regions. From Gustafsson et al. Mol Cell Biol. 32(13):2440-53, 2012
Fig. 2. ANK54 is an ankyrin repeat, nucleocytoplasmic protein, colocalizing with BTK in the cytoplasm, inner membrane, and perinuclear regions. From Gustafsson et al. Mol Cell Biol. 32(13):2440-53, 2012. Photo: N/A
Illustration of Fig. 3 Schematic representation of the ITK-SYK fusion gene. From Hussain et al. Biochem Biophys Res Commun. 390(3):892-6, 2009.
Fig. 3 Schematic representation of the ITK-SYK fusion gene. From Hussain et al. Biochem Biophys Res Commun. 390(3):892-6, 2009. Photo: N/A