Clinical and Genetic Analyses of SPG7 in Japanese Patients with Undiagnosed Ataxia.

Objective Spastic paraplegia 7 (SPG7) is an autosomal recessive neurodegenerative disorder caused by biallelic pathogenic variants in SPG7. It is predominantly characterized by adult-onset slowly progressive spastic paraparesis. While SPG7 presenting with ataxia with or without spasticity is relatively common in Europe and North America, it is considered rare in Japan.

Thioredoxin and TRAF family proteins regulate reactive oxygen species-dependent activation of ASK1 through reciprocal modulation of the N-terminal homophilic interaction of ASK1.

Apoptosis signal-regulating kinase 1 (ASK1), a member of the mitogen-activated protein kinase kinase kinase family, plays pivotal roles in reactive oxygen species (ROS)-induced cellular responses. In resting cells, endogenous ASK1 constitutively forms a homo-oligomerized but still inactive high-molecular-mass complex including thioredoxin (Trx), which we designated the ASK1 signalosome. Upon ROS stimulation, the ASK1 signalosome unbinds from Trx and forms a fully activated higher-molecular-mass complex, in part by recruitment of tumor necrosis factor receptor-associated factor 2 (TRAF2) and TRAF6.

GTP binding is essential to the protein kinase activity of LRRK2, a causative gene product for familial Parkinson's disease.

Leucine-rich repeat kinase 2 (LRRK2), a product of a causative gene for the autosomal-dominant form of familial Parkinson's disease (PARK8), harbors a Ras-like small GTP binding protein-like (ROC) domain besides the kinase domain, although the relationship between these two functional domains remains elusive. Here we show by thin-layer chromatographic analysis that LRRK2 stably binds GTP but lacks a GTPase activity in HEK293 and Neuro-2a cells. A ROC domain mutation that converts LRRK2 to a guanine nucleotide-free form (T1348N) abolishes the kinase activity of LRRK2 as well as its phosphate incorporation upon metabolic labeling.

Thioredoxin and protein kinases in redox signaling.

Reactive oxygen species (ROS) play critical roles for the determination of cell fate by eliciting a wide variety of cellular responses, such as proliferation, differentiation and apoptosis. Many intracellular signaling pathways involved in such ROS-induced cellular responses are regulated by the intracellular redox state, which depends on the balance between the levels of oxidizing and reducing equivalents. Recently, increasing attention has been paid to the roles of thioredoxin (Trx) as a signaling intermediate beyond its intrinsic antioxidant activity.