The molecular functions and pathophysiologic role of the lymphocyte α-kinase gene (ALPK1) in gout are unknown. We aimed to examine ALPK1 expression in patients with gout and investigate its role in monosodium urate monohydrate (MSU)-induced inflammatory responses. Microarray data mining was performed with six datasets containing three clinical gout and three volunteer samples. Real-time quantitative polymerase chain reaction (qPCR) assay was used to profile ALPK1 mRNA expression in 62 independent samples. RNA interference for ALPK1 suppression in THP1 cells (human monocytic cell line) was used to scrutinize the functional role of ALPK1 in MSU-mediated inflammatory responses, and ALPK1 expression in MSU-treated THP1 cells was determined by qPCR and Western blot analysis. Cytokine mRNA expression in HEK293 cells after incubation with different concentrations of MSU crystals in the presence or absence of ALPK1 was also detected by qPCR, and ERK1/2, p38, and JNK expressions were investigated by Western blot analysis. ALPK1 mRNA was overexpressed in the clinical gout samples. MSU treatment promoted ALPK1 expression at the mRNA and protein levels. Furthermore, ALPK1 knockdown in THP1 cells resulted in a markedly decreased IL-1β, TNF-α, and IL-8 mRNA expression; plasmid ALPK1 transfection and MSU stimulation synergistically increased the mRNA expression of these cytokines in a concentration-dependent manner. The synergistic effect also led to ERK1/2 activation. ALPK1 is a gout-susceptible gene involved in MSU-induced inflammatory responses. It may contribute to the development of gout by enhancing the inflammatory responses via the mitogen-activated protein kinase pathway.

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Gout is characterized by the monosodium urate monohydrate (MSU)-induced arthritis. Alpha kinase-1 (ALPK1) has shown to be associated with MSU-induced inflammation and gout. Here, we used bioinformatics, proteomics, cell models, and twenty in vitro human assays to clarify some of its role in the inflammatory response to MSU. We found myosin IIA to be a frequent interacting protein partner of ALPK1, binding to its N-terminal and forming a protein complex with calmodulin and F-actin, and that MSU-induced ALPK1 phosphorylated the myosin IIA. A knockdown of endogenous ALPK1 or myosin IIA significantly reduced the MSU-induced secretion of tumour necrosis factor (TNF)-α. Furthermore, all gouty patients expressed higher basal protein levels of ALPK1, myosin IIA, and plasma TNF-α, however those medicated with colchicine has shown reduced myosin IIA and TNF-α but not ALPK1. The findings suggest ALPK1 is a kinase that participates in the regulation of Golgi-derived TNF-α trafficking through myosin IIA phosphorylation in the inflammation of gout. This novel pathway could be blocked at the level of myosin by colchicine in gout treatment.

Alpha-kinase 1 (ALPK1) is associated with chronic kidney disease (CKD), type 2 diabetes mellitus and gout. Elevated ALPK1 levels have been observed in the kidneys of patients with diabetes and the white blood cells of patients with gout. As renal injury is a common outcome of CKD, diabetes and gout, the aim of this study was to investigate the effect of ALPK1 in the development of renal injury in a hyperglycemic condition. Hyperglycemia was induced in wild-type and ALPK1 transgenic mice by an intraperitoneal injection of streptozotocin (STZ). Functional and histological examinations were performed after 3weeks. STZ-treated ALPK1 transgenic mice exclusively showed arteriolar sclerosis and fibrous thickening of the Bowman's capsule in the kidney. This was accompanied by body weight loss, severe hyperglycemia, and low serum insulin levels. Renal renin and serum renin protein levels were higher in STZ-treated ALPK1 transgenic mice, whereas cGKII protein level was decreased by ALPK1 in human embryonic kidney 293 (HEK293) cells. ALPK1 up-regulated TGF-beta1 levels and transcription of fibrosis-related genes, including MMP-9, FIBRONECTIN, and TIMP1. MSU crystals increased ALPK1 transcription in cultured kidney cells. Finally, ALPK1 enhanced production of MSU crystals-induced IL-1beta in mice. Stimulation of soluble sodium urate induced IL-1beta and Alpk1 mRNA production in mice kidney. Taken together, these data show that an increase in ALPK1 results in accelerated fibrotic nephropathies, primarily through the enhancement of renin, TGF-beta1, and IL-1beta. Renal or blood ALPK1 levels are involved in the induction of fibrotic renal injury in an experimental model of hyperglycemia.

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