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Molecular cloning and characterization of a novel human STE20-like kinase, hSLK
E Yamada1, K Tsujikawa, S Itoh
1Department of Immunology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka, Japan.
Abstract:
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 kinase for which the kinase domain located at the N-terminus shares considerable homology to that of the STE20-like kinase family. The C-terminal domain 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 characteristic of the p21-activated kinase (PAK) family, polyproline consensus binding sites, or the Leu-rich domain seen in the group I germinal center kinases (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 kinase MAPK (ERK, JNK/SAPK and p38) pathways. Moreover, hSLK kinase activity is not upregulated by constitutive active forms of GTPases (RasV12, RacV12 and Cdc42V12). These structural and functional properties indicate that hSLK should be considered to be a new member of group II GCKs.
Insights
We identified a novel human STE20-like kinase (hSLK) involved in cell signaling. This serine/threonine kinase, hSLK, is ubiquitously expressed and functions as a new member of group II germinal center kinases (GCKs).
Area of Science:
- Molecular Biology
- Cell Signaling
Background:
- The STE20-like kinase family plays crucial roles in various cellular processes.
- Understanding novel kinases is essential for deciphering complex signaling networks.
Purpose of the Study:
- To clone and characterize a human homolog of guinea pig STE20-like kinase.
- To investigate the structural and functional properties of the novel human SLK (hSLK).
Main Methods:
- Cloning of hSLK cDNA from a human lung carcinomatous cell line (A549).
- Sequence analysis to identify conserved domains and structural features.
- Expression and in vitro kinase assays using COS-7 cells and myelin basic protein.
- Analysis of hSLK's interaction with mitogen-activated protein kinase (MAPK) pathways and GTPases.
Main Results:
- hSLK encodes a 1204 amino acid serine/threonine kinase with homology to STE20-like kinases.
- The C-terminal domain of hSLK contains a coiled-coil structure and PEST sequences, but lacks GBD, polyproline, and Leu-rich domains.
- hSLK exhibits autophosphorylation and phosphorylates myelin basic protein.
- hSLK does not activate ERK, JNK/SAPK, or p38 MAPK pathways and is not upregulated by RasV12, RacV12, or Cdc42V12.
Conclusions:
- hSLK represents a novel kinase distinct from p21-activated kinases (PAKs) and group I germinal center kinases (GCKs).
- Based on its structural and functional characteristics, hSLK is classified as a new member of group II GCKs.
- Further research into hSLK's role in cellular signaling is warranted.