Molecular clotting and characterization of a novel human STE20-like kinase, hSLK

We have cloned a human counterpart to a guinea pig STE20-like kinase cDNA, designated human SLK (hSLK), from a human lung carcinomatous cell line A549 cDNA library, hSLK cDNA encodes a novel 1204 amino acid serine/threonine k inase for which the kinase domain located at the N-terminus shares consider able homology to that of the STE20-like kinase family. The C-terminal domai n of hSLK includes both the coiled-coil structure and four Pro/Glu/Ser/Thr- rich (PEST) sequences, but not the GTPase-binding domain (GBD) that is char acteristic of the p21-activated kinase (PAK) family, polyproline consensus binding sites, or the Leu-rich domain seen in the group I germinal center k inases (GCKs). Northern blot analysis indicated that hSLK was ubiquitously expressed. hSLK overexpressed in COS-7 cells phosphorylates itself as well as myelin basic protein used as a substrate. On the other hand, hSLK cannot activate any of the three well-characterized mitogen-activated protein kin ase MAPK (ERI, JNK/SAPK and p38) pathways. Moreover, hSLK kinase activity i s not upregulated by constitutive active forms of GTPases (RasV12, RacV12 a nd Cdc42V12). These structural and functional properties indicate that hSLK should be considered to be a new member of group II GCKs. (C) 2000 Elsevie r Science B.V. All rights reserved.