SDF1α‐induced interaction of the adapter proteins Nck and HS1 facilitates actin polymerization and migration in T cells

Abstract

Noncatalytic region of tyrosine kinase (Nck) is an adapter protein that comprises one SH2 (Src homology) domain and three SH3 domains. Nck links receptors and receptorassociated tyrosine kinases or adapter proteins to proteins that regulate the actin cytoskeleton. Whereas the SH2 domain binds to phosphorylated receptors or associated phosphoproteins, individual interactions of the SH3 domains with proline-based recognition motifs result in the formation of larger protein complexes. In T cells, changes in cell polarity and morphology during T-cell activation and effector function require the T-cell receptor-mediated recruitment and activation of actin-regulatory proteins to initiate cytoskeletal reorganization at the immunological synapse. We previously identified the adapter protein HS1 as a putative Nck-interacting protein. We now demonstrate that the SH2 domain of Nck specifically interacts with HS1 upon phosphorylation of its tyrosine residue 378. We report that in human T cells, ligation of the chemokine receptor CXCR4 by stromal cell-derived factor 1α (SDF1α) induces a rapid and transient phosphorylation of tyrosine 378 of HS1 resulting in an increased association with Nck. Consequently, siRNA-mediated downregulation of HS1 and/or Nck impairs SDF1α-induced actin polymerization and T-cell migration.Keywords: CXCR4 r HS1 r Nck r SDF1α r T cells IntroductionT cells govern adaptive immunity by cytokine secretion or cytotoxic effector function. After development in the thymus, naive T lymphocytes constantly recirculate between the blood stream and lymphoid tissues. At the molecular level, this homing and migration processes rely on complex interactions of selected chemokines with their receptors on respective T cells and of T-cell adhesion molecules binding to their ligands on endothelial cells or the extracellular matrix. Individual interactions elicit specific signaling pathways that induce dynamic cytoskeletal rearrangements, which enable lymphocytes to adhere to or pass a certain substrate or to transmigrate through a given endothelium. Morphologically, circular floating T cells adopt a migratory phenotype characterized Correspondence: Dr. Marcus Lettau e-mail: lettau@immunologie.uni-kiel.de by a leading edge at the front and an uropod at the rear. When T cells encounter their antigen on an antigen-presenting cell in the lymph nodes or spleen, migration is halted and the cells rapidly polarize toward the intercellular contact area. The subsequent formation of the so-called immunological synapse (IS) is again accompanied by complex cytoskeletal changes and comprises the structural basis for T-cell activation. This primary antigenic stimulation ultimately results in cell-cycle progression, clonal expansion, and differentiation to T-effector cells. The activated T cells regain migratory potential, leave the lymphoid tissue, and search the periphery for infected or transformed cells displaying their cognate antigen. Upon antigen encounter, the T cells adhere to their target cell and polarize toward the intercell...

Wnt5a induces ROR1 to complex with HS1 to enhance migration of chronic lymphocytic leukemia cells

“…For sure, HS1 does plays such a role in hemapoietic cells that lack expression of ROR1, possibly through its capacity to interact with other surface receptors, which, upon activation, require reorganization of the actin cytoskeleton for migration or cognate cell–cell interactions. 15 , 16 , 21 , 31 Indeed, HS1 can associate with the Arp2/3 complex to facilitate F-actin polymerization. 13 , 14 HS1-deficient T-cells have impaired cell motility, 16 and fail to accumulate F-actin at the immune synapse.…”

“… 15 , 16 , 21 , 31 Indeed, HS1 can associate with the Arp2/3 complex to facilitate F-actin polymerization. 13 , 14 HS1-deficient T-cells have impaired cell motility, 16 and fail to accumulate F-actin at the immune synapse. 38 Moreover, dendritic cells from mice made deficient in HS1 (HS1 −/− ) have aberrant lamellipodial dynamics, loosely packed podosome arrays and impaired directional migration.…”

“…HS1 is a cytoplasmic protein that can be undergo tyrosine phosphorylation and promote polymerization and rearrangement of the actin cytoskeleton required for cell migration. 13 , 14 , 15 , 16 , 17 HS1 also contains an SH3 domain, which allows it to bind characteristic motifs (-P-X-X-P-), which often are found in the proline-rich domains (PRDs) of other proteins. 18 , 19 , 20 HS1 also is expressed in CLL cells.…”

Hematopoietic cell-specific lyn substrate (HCLS1 or HS1): A versatile actin-binding protein in leukocytes

“…This phosphorylation allows anchoring to the SH3 domain of the adaptor protein noncatalytic region of tyrosine kinase (Nck), whose interaction supports the polymerization of actin induced by CXCL12. The joint function of HS1 and Nck in the regulation of actin during chemotaxis was confirmed in transwell assays where the absence of HS1, Nck, or both, resulted in decreased migration toward a CXCL12 gradient . However, it remains to be determined which kinase is responsible for CXCL12‐induced HS1 phosphorylation in this context.…”

“…The joint function of HS1 and Nck in the regulation of actin during chemotaxis was confirmed in transwell assays where the absence of HS1, Nck, or both, resulted in decreased migration toward a CXCL12 gradient. 25 However, it remains to be determined which kinase is responsible for CXCL12-induced HS1 phosphorylation in this context.…”