The calponin homology domain of Vav1 associates with calmodulin and is prerequisite to T cell antigen receptor-induced calcium release in Jurkat T lymphocytes.
Vav1 is a guanine nucleotide exchange factor that is expressed specifically in hematopoietic cells and plays important roles in T cell development and activation. Vav1 consists of multiple structural domains so as to facilitate both its guanine nucleotide exchange activity and scaffold function following T cell antigen receptor (TCR) engagement. Previous studies demonstrated that the calponin homology (CH) domain of Vav1 is required for TCR-stimulated calcium mobilization and thus downstream activation of nuclear factor of activated T cells. However, it remained obscure how Vav1 functions in regulating calcium flux. In an effort to explore molecules interacting with Vav1, we found that calmodulin bound to Vav1 in a calcium-dependent and TCR activation-independent manner. The binding site was mapped to the CH domain of Vav1. Reconstitution of vav1-null Jurkat T cells (J.Vav1) with CH-deleted Vav1 exhibited a severe deficiency in calcium release to the same extent as that of Jurkat cells treated with the calmodulin inhibitor or J.Vav1 cells. The defect persisted even when phospholipase-Cgamma1 was fully activated, indicating a prerequisite role of Vav1 CH domain in calcium signaling. The results suggest that Vav1 and calmodulin function cooperatively to potentiate TCR-induced calcium release. This study unveiled a mechanism by which the Vav1 CH domain is involved in calcium signaling and provides insight into our understanding of the role of Vav1 in T cell activation.
Zhou
Zhuo
Z
Department of Biochemistry and Molecular Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.
Yin
Jie
J
Dou
Zhixun
Z
Tang
Jun
J
Zhang
Cuizhu
C
Cao
Youjia
Y
D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry*; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D008840:Microfilament Proteins / Q000737:chemistry*; D008954:Models, Biological; D051966:Phospholipase C gamma / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051567:Proto-Oncogene Proteins c-vav / Q000737:chemistry* / Q000502:physiology*; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry*; D013601:T-Lymphocytes / Q000378:metabolism; D013997:Time Factors; D000096985:Calponins
D002118:Calcium; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008840:Microfilament Proteins; D051966:Phospholipase C gamma; D051567:Proto-Oncogene Proteins c-vav; D011948:Receptors, Antigen, T-Cell; D000096985:Calponins; C496618:VAV1 protein, human