SH3 domain of Bruton's tyrosine kinase can bind to proline-rich peptides of TH domain of the kinase and p120cbl

Abstract

X-linked agammaglobulinemia (XLA), an inherited disease, is caused by mutations in the Bruton's tyrosine kinase (BTK). The absence of functional BTK leads to failure of B-cell differentiation; this incapacitates antibody production in XLA patients, who suffer from recurrent, sometimes lethal, bacterial infections. BTK plays an important role in B-cell development; it interacts with several proteins in the context of signal transduction. Point mutation in the BTK gene that leads to deletion of C-terminal 14 aa residues of BTK SH3 domain was found in a patient family. To understand the role of BTK, we studied binding of BTK SH3 domain (aa 216-273, 58 residues) and truncated SH3 domain (216-259, 44 residues) with proline-rich peptides; the first peptide constitutes the SH3 domain of BTK, while the latter peptide lacks 14 amino acid residues of the C terminal. Proline-rich peptides selected from TH domain of BTK and p120cbl were studied. It is known that BTK TH domain binds to SH3 domains of various proteins. We found that BTK SH3 domain binds to peptides of BTK TH domain. This suggests that BTK SH3 and TH domains may associate in inter- or intramolecular fashion, which raises the possibility that the kinase may be regulating its own activity by restricting the availability of both its ligand-binding modules. We also found that truncated SH3 domain binds to BTK TH domain peptide less avidly than does normal SH3 domain. Also, we show that the SH3 and truncated SH3 domains bind to peptide of p120cbl, but the latter domain binds weakly. It is likely that the truncated SH3 domain fails to present to the ligand the crucial residues in the correct context, hence the weaker binding. These results delineate the importance of C-terminal in binding of SH3 domains and indicate also that improper folding and the altered binding behavior of mutant BTK SH3 domain likely leads to XLA.

The Transcription FactorBrightAssociates with Bruton’s Tyrosine Kinase, the Defective Protein in Immunodeficiency Disease

“…While the important role Btk plays immediately after Ig receptor signaling is well documented, it may have additional functions. It associates with several proteins, including protein kinase C (36), G proteins (37,38), c-Cbl (39), and a few Src-type kinases (40,41). In addition, Btk phosphorylates the transcription factor BAP135, or transcription factor II-I (TFII-I), in activated B lymphocytes and may regulate its activity (42)(43)(44).…”

Stability and Peptide Binding Specificity of BTK SH2 Domain: Molecular Basis for X-Linked Agammaglobulinemia

“…domain, and a catalytic tyrosine kinase domain~Yu & Schreiber, 1994;Cohen et al, 1995;Pawson, 1995;Shokat, 1995!. The exact function of the PH domain in signaling proteins is still unknown, but it is thought to effect protein-protein interactions and0or membrane localization~Cohen et al, 1995;Pawson, 1995;Shokat, 1995!. The SH3 and SH2 domains are small protein modules that mediate protein-protein interactions and occur in many proteins involved in intracellular signal transduction~Yu & Schreiber, 1994;Cohen et al, 1995;Pawson, 1995;Shokat, 1995!. It has been reported that SH3 domains bind to proline-rich sequences and SH2 domains bind to phosphotyrosine sequences of the receptor protein tyrosine kinases~Kuriyan & Cowburn, 1993; Pawson & Schlessinger, 1993;Songyang et al, 1993;Sudol, 1998!. Although the importance of the PH and SH3 domains of Btk has been documented on the basis of their structural and functional roles in the B-cell development~Cheng et al, 1994;Tsukada et al, 1994;Yao et al, 1994;Zhu et al, 1994;Cory et al, 1995;Vihinen et al, 1995;Hyvonen & Saraste, 1997;Patel et al, 1997;Hansson et al, 1998;Baraldi et al, 1999;Morrogh et al, 1999;Nore et al, 2000;Tzeng et al, 2000!, little is known about its SH2 domain. It was shown that the Btk SH2 domain is essential for phospholipase C-g phosphorylation~Takata & Kurosaki, 1996;Fluckiger et al, 1998;Scharenberg et al, 1998!…”

Stability and peptide binding specificity of Btk SH2 domain: Molecular basis for X‐linked agammaglobulinemia

“…domain, and a catalytic tyrosine kinase domain~Yu & Schreiber, 1994;Cohen et al, 1995;Pawson, 1995;Shokat, 1995!. The exact function of the PH domain in signaling proteins is still unknown, but it is thought to effect protein-protein interactions and0or membrane localization~Cohen et al, 1995;Pawson, 1995;Shokat, 1995!. The SH3 and SH2 domains are small protein modules that mediate protein-protein interactions and occur in many proteins involved in intracellular signal transduction~Yu & Schreiber, 1994;Cohen et al, 1995;Pawson, 1995;Shokat, 1995!. It has been reported that SH3 domains bind to proline-rich sequences and SH2 domains bind to phosphotyrosine sequences of the receptor protein tyrosine kinases~Kuriyan & Cowburn, 1993;Pawson & Schlessinger, 1993;Songyang et al, 1993;Sudol, 1998!. Although the importance of the PH and SH3 domains of Btk has been documented on the basis of their structural and functional roles in the B-cell development~Cheng et al, 1994;Tsukada et al, 1994;Yao et al, 1994;Zhu et al, 1994;Cory et al, 1995;Vihinen et al, 1995;Hyvonen & Saraste, 1997;Patel et al, 1997;Hansson et al, 1998;Baraldi et al, 1999;Morrogh et al, 1999;Nore et al, 2000;Tzeng et al, 2000!, little is known about its SH2 domain. It was shown that the Btk SH2 domain is essential for phospholipase C-g phosphorylation~Takata & Kurosaki, 1996;Fluckiger et al, 1998;Scharenberg et al, 1998!…”