Given an abstract from a research paper, your task is to identify and label relationships between chemical compounds and genes mentioned in the abstract.

The relationship type must be one of ['DOWNREGULATOR', 'SUBSTRATE', 'INDIRECT-REGULATOR', 'PART-OF', 'MODULATOR-ACTIVATOR', 'REGULATOR', 'INHIBITOR', 'COFACTOR', 'UPREGULATOR', 'ACTIVATOR', 'ANTAGONIST', 'NOT', 'INDIRECT-DOWNREGULATOR', 'SUBSTRATE_PRODUCT-OF', 'INDIRECT-UPREGULATOR', 'AGONIST', 'PRODUCT-OF', 'MODULATOR', 'DIRECT-REGULATOR', 'UNDEFINED', 'AGONIST-INHIBITOR', 'AGONIST-ACTIVATOR', 'MODULATOR-INHIBITOR'].

Please format your output as a JSON array. Each entry in the array should express a single relation, formatted as ["<Entity_A>", "<RELATION_A_B>", "<Entity_B>"]. If no relations can be found, please output an empty JSON array [].

Abstract:

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.
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