MST/MLK2, a member of the mixed lineage kinase family, directly phosphorylates and activates SEK1, an activator of c-Jun N-terminal kinase/stress-activated protein kinase.
Abstract
c-Jun N-terminal kinases/stress-activated protein kinases (JNKs/SAPKs) are mitogen-activated protein kinase (MAPK)-related protein kinases that are involved in several cellular events, including growth, differentiation, and apoptosis. Mixed lineage kinases (MLKs) form a family of protein kinases sharing two leucine zipper-like motifs and a kinase domain whose primary structure is similar to both the tyrosine-specific and the serine/threonine-specific kinase classes. We have reported that a member of the MLK family, MUK/DLK/ZPK, can activate JNK/SAPK in vivo, and here we show that another member of the MLK family, MST/MLK2, activates JNK/SAPK. Both MUK/DLK/ZPK and MST/MLK2 cause a slight activation of p38/Mpk2 when overexpressed in COS-1 cells, whereas MST/MLK2, but not MUK/DLK/ZPK, activates extracellular response kinase (ERK) to a certain degree. The activity of SEK1/MKK4/JNKK, a MAPK kinase class protein kinase designated as a direct activator of JNK/SAPK, is also induced by MUK/DLK/ZPK or MST/MLK2 overexpression. Furthermore, recombinant MST/MLK2 produced in bacteria directly phosphorylates and activates SEK1/MKK4/JNKK in vitro, showing that MST/MLK2 acts like a MAPK kinase kinase. Taken together, these results suggest that ...Continue Reading
References
A conserved binding motif defines numerous candidate target proteins for both Cdc42 and Rac GTPases.
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Citations
Selective expression of JNK isoforms and stress-specific JNK activity in different neural cell lines
Regulation of apoptotic c-Jun N-terminal kinase signaling by a stabilization-based feed-forward loop
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Apoptosis
Apoptosis is a specific process that leads to programmed cell death through the activation of an evolutionary conserved intracellular pathway leading to pathognomic cellular changes distinct from cellular necrosis