WNK1 Activates ERK5 by an MEKK2/3-dependent Mechanism

Abstract

WNK1 belongs to a unique protein kinase family that lacks the catalytic lysine in its normal position. Mutations in human WNK1 and WNK4 have been implicated in causing a familial form of hypertension. Here we report that overexpression of WNK1 led to increased activity of cotransfected ERK5 in HEK293 cells. ERK5 activation was blocked by the MEK5 inhibitor U0126 and expression of a dominant negative MEK5 mutant. Expression of dominant negative mutants of MEKK2 and MEKK3 also blocked activation of ERK5 by WNK1. Moreover, both MEKK2 and MEKK3 coimmunoprecipitated with endogenous WNK1 from cell lysates. WNK1 phosphorylated both MEKK2 and -3 in vitro, and MEKK3 was activated by WNK1 in 293 cells. Finally, ERK5 activation by epidermal growth factor was attenuated by suppression of WNK1 expression using small interfering RNA. Taken together, these results place WNK1 in the ERK5

Axon Transport and Neuropathy

“…92 Similarly, mutations in WNK1 could also alter NGF/TrkA signaling through its protein kinase activity, although abnormalities in kinase activity for particular substrates have not been examined in detail in mutant proteins that contain the pathogenic exon 8B. 93 Nevertheless, WNK1 activates Erk5, 94 and Erk5 is a critical mitogen-activated protein kinase required for retrograde NGF/TrkA survival signaling in NGF-dependent neurons. 95 Alterations in WNK1-mediated activation of Erk5 could lead to altered sensory and sympathetic neuron survival in HSAN2 caused by WNK1 mutations.…”

WNKs: protein kinases with a unique kinase domain

“…WNK1 partially co-localizes with and phosphorylates synaptotagmin 2, a protein involved in vesicle exocytosis and endocytosis (Lee et al, 2004). Phosphorylation by WNK1 changes the requirement for calcium to induce binding of synaptotagmin 2 to phospholipid vesicles.…”

“…The catalytic lysine of WNKs and other protein kinases, despite being localized in different parts of the kinase domain, both point toward the active site in the cleft (Figure 2). WNK kinases catalyze the phosphorylation of endogenous and exogenous substrates (Xu et al, 2000(Xu et al, , 2004Lenertz et al, 2005;He et al, 2007). Thus, WNKs are bona fide protein kinases.…”

Similar effects of all WNK3 variants on SLC12 cotransporters

“…WNKs have been proposed to have many functions besides the modulation of electroneutral cation-coupled chloride cotransporters, including regulating basic cellular processes such as mitosis (25), apoptosis (27) and neoplastic transformation (19), regulating synaptagmin 2 (15), and interacting with many other kinases, like TGF-␤ (14), MAP kinases (31), and the STE20-related alanine/proline-rich kinases SPAK and OSR1 (28) (for an excellent review, see Ref. 16).…”