Characterization of ERK Activation in Human Mast Cells Stimulated by Contact with T Cells

Abstract

Close physical proximity between mast cells and T cells has been demonstrated in several human conditions. We have identified and characterized a novel mast cell activation pathway initiated by contact with T cells, and showed that this pathway is associated with cytokine release. It has been shown recently that Ras is activated in this pathway. Thus, in the present study we further explore the downstream events associated with Ras activation and cytokine release in human mast cells stimulated by contact with T cells. ERK activation in human mast cells stimulated by either contact with T cells or by crosslinking the FC epsilon receptor was studied. Photobleaching experiments were used to study ERK localization. Enzyme linked immunosorbent assay was used to study the cytokine release by human mast cells. We show that stimulation of human mast cells by contact with activated T cells results is sustained ERK activation. Furthermore, sustained ERK activation in these cells is associated with increased dwell time at the nucleus and with IL-8 release. Interestingly, when mast cells were stimulated by crosslinking the FC epsilon receptor I, ERK activation was transient. ERK activation was associated with a shorter dwell time at the nucleus and with TNF-alpha release. Thus, retaining ERK in the nucleus might be a mechanism utilized by human mast cells to generate different cytokines from a single signaling cascade.

T Cell-Induced Mast Cell Activation: A Role for Microparticles Released from Activated T Cells

“…We recently showed that direct contact of human mast cells with T lymphocyte membranes resulted in the phosphorylation of the MAPK family (15,16). The MAPKs are known to play an important role in mediator release in human mast cells after IgEcross-linking or on activation by inducers, such as SCF and TNF-a (20,21).…”

“…It was shown recently that stimulation of human mast cells by contact with activated T cells is associated with Ras activation and phosphorylation of the mitogen-activated MAPKs ERK (15,16). Therefore, we investigated whether microparticles derived from activated T cells were also able to induce ERK activation.…”

The Involvement of Protein Kinase D in T Cell-Induced Mast Cell Activation

“…We have previously shown that stimulation of MC by T*m leads to degranulation and release of certain cytokines [1,2,3], and is associated with the phosphorylation of ERK and p38 [5]. The PKD family has been implicated in diverse cellular functions [7].…”

“…Recent studies have shown that heterotypic adhesion of MC to activated but not resting T cells induces MC degranulation and cytokine production in a pathway associated with the activation of Ras and the MAPK signaling pathway [1,2,3,4,5]. …”

“…We have previously shown that direct contact with activated but not resting T cells, or their membranes or microvesicles, resulted in MC degranulation and the production of various cytokines such as IL-8, oncostatin M (OSM) and IL-24 [1,2,3,4]. This pathway is also associated with the activation of ERK and p38 [5]. …”