| Leukocyte migration and trafficking is dynamically regulated by various chemokine and adhesion molecules and is vital to the proper formation of the immune system and its function. The signaling protein Chat-H is highly expressed in lymphoid organs, yet its role in immune cell function has not been characterized. To address this question, I optimized a lentiviral RNAi system to knockdown Chat-H from T lymphocytes. My data reveal an essential role for the signaling protein Chat-H as a critical regulator of T lymphocyte migration. Impaired migration of Chat-H deficient cells coincided with defective tyrosine- and serine/threonine phosphorylation of its constitutive binding partner CasL and defective inside-out signaling as shown by diminished chemokine-induced activation of the Rap-1 GTPase and integrin-mediated adhesion. Furthermore, Chat-H was found to be broadly expressed in hematopoietic lineages, and deficiency in Chat-H expression inhibited bone marrow engraftment, shown by a dramatic reduction in the development of hematopoietic cell lineages. These results identify Chat-H as a critical signaling intermediate acting upstream of Rap1 in chemokine-induced adhesion and migration, and preliminary results from other systems suggest that Chat-H may be important for both phagocytosis and neural development. |
