Germinal Center Kinase–like Kinase Overexpression in T Cells as a Novel Biomarker in Rheumatoid Arthritis

Abstract

Objective Germinal center kinase–like kinase (GLK; also called MAPKKKK‐3) activates protein kinase Cθ (PKCθ) during T cell activation and controls autoimmunity in lupus patients. Intracellular kinases are involved in the pathogenesis of rheumatoid arthritis (RA). We undertook this study to determine the role of GLK in RA. Methods The severity of collagen‐induced arthritis (CIA) was studied in GLK‐deficient mice. Expression levels of GLK from RA patients were determined by Western blotting, flow cytometry, real‐time polymerase chain reaction, and immunohistochemical staining. Localization of GLK in T cells was identified by confocal microscopy. RA disease activity was assessed using the Disease Activity Score in 28 joints. Results GLK‐deficient mice displayed impaired CIA development and decreased inflammatory cytokine levels. Local T cell infiltration and collagen restimulation responses were impaired by GLK deficiency. RA patients showed significantly higher GLK protein and messenger RNA levels in peripheral blood T cells than did healthy controls. GLK‐overexpressing T cells in synovial fluid and synovial tissue samples from RA patients were increased compared with those from osteoarthritis patients. Confocal microscopy and flow cytometry showed that GLK colocalized and coexisted with phosphorylated PKCθ in T cells from RA patients. Frequencies of GLK‐expressing T cells were significantly correlated with RA disease activity. Conclusion GLK overexpression in T cells contributes to the pathogenesis of RA, indicating that GLK is a novel biomarker for autoimmune disease severity and a potential therapeutic target for RA.

AhR–ROR‐γt complex is a therapeutic target for MAP4K3/GLK high IL‐17A high subpopulation of systemic lupus erythematosus

“…GLK overexpression in T cells is involved in the pathogenesis of several human autoimmune diseases, including SLE (21), RA (23), and adult-onset Still’s disease (22). The GLK–AhR–ROR-γt–IL-17A signaling identified using murine T cells (18) is further verified in this study using purified T cells from human patients with SLE.…”

“…At 12 wk of age (d 0), male C57BL/6J mice were intradermally injected in the superficial layer of tail dermis with a total of 100 μl of an emulsion containing the chicken type II chicken collagen or Freund’s complete adjuvant emulsification (MD Biosciences, Oakdale, MN, USA) (23). The same injection was repeated intraperitoneally on d 21.…”

“…GLK induces T-cell activation through phosphorylating and activating PKC-θ (21). Moreover, GLK overexpression occurs in peripheral blood T cells from patients with SLE, RA, or adult-onset Still’s disease; the frequencies of GLK-overexpressing T cells are correlated with autoimmune disease severity (21–23). Recently, using T-cell–specific, GLK-transgenic (Lck-GLK Tg) mice, we found that GLK overexpression selectively induces IL-17A overproduction in T cells, leading to autoimmune responses (18).…”

GLK/MAP4K3 overexpression associates with recurrence risk for non-small cell lung cancer

“…Mitogen-activated protein kinase kinase kinase kinase (MAP4K) family — including HPK1/MAP4K1 [7, 8], GCK/MAP4K2, GLK/MAP4K3 [9–12], HGK/MAP4K4 [13–15], and KHS/MAP4K5 — is a subgroup of the mammalian STE20 family of serine/threonine protein kinases [16, 17]. MAP4K family kinases are the upstream regulators of the MAP kinase cascades that regulate various cellular functions, such as proliferation, apoptosis, and migration [18, 19].…”

“…GLK can promote cell growth via activating the mTOR signaling pathway after amino acid treatment in epithelial cell lines. GLK positively regulates NF-κB signaling, leading to the development of autoimmune diseases [10–12, 26]. Activation of the NF-κB signaling pathway is involved in carcinogenesis and in cancer resistance to chemotherapy or radiation therapy [27, 28].…”