Cloning and characterization of a testis and brain-specific isoform of mouse 3'-phosphoinositide-dependent protein kinase-1, mPDK-1 beta.
3'-Phosphoinositide-dependent protein kinase-1 (PDK-1) phosphorylates and activates members of the protein kinase AGC family and plays a key role in receptor tyrosine kinase signaling. Here we report the cloning and characterization of a splice variant of mouse PDK-1, mPDK-1 beta. The cDNA encoding mPDK-1 beta contains two alternative start codons and translation from these start codons generates proteins that are, respectively, 27 or 51 amino acid residues shorter at the amino-terminus than the previously identified PDK-1 isolated from mouse liver (now renamed mPDK-1 alpha) [J. Biol. Chem. 274 (1999) 8117]. Analysis of mouse tissues shows that mPDK-1 beta is highly expressed in the testis and various functional regions of the brain. Expression of this isoform is increased in the brain of aged mice. Both mPDK-1 alpha and mPDK-1 beta are autophosphorylated at both serine and threonine residues in vitro and showed similar levels of tyrosine phosphorylation when co-expressed with either constitutively active Src or Fyn tyrosine kinases in cells. However, the mPDK-1 isoforms showed significant differences in their response to pervanadate- or insulin plus vanadate-stimulated tyrosine phosphorylation. Taken together, our findings suggest that the two PDK-1 isoforms may be differentially regulated in cells. The specific expression of mPDK-1 beta in mouse testis and brains of aged mice also suggests potential involvement of this kinase in regulating animal spermatogenesis and aging.
Dong
Lily Q
LQ
Department of Pharmacology, The University of Texas Health Science Center, San Antonio, TX 78229, USA. dongq@uthscsa.edu
Ramos
Fresnida J
FJ
Wick
Michael J
MJ
Lim
Mei Ann
MA
Guo
Zhongmao
Z
Strong
Randy
R
Richardson
Arlan
A
Liu
Feng
F
D064413:3-Phosphoinositide-Dependent Protein Kinases; D000375:Aging; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000201:enzymology*; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D005260:Female; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn; D016415:Sequence Alignment; D013091:Spermatogenesis; D013737:Testis / Q000201:enzymology*; D014443:Tyrosine / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology; D019061:src-Family Kinases / Q000378:metabolism
D007328:Insulin; D007527:Isoenzymes; D011518:Proto-Oncogene Proteins; C076715:pervanadate; D014638:Vanadates; D014443:Tyrosine; C494957:FYN protein, human; C494960:Fyn protein, mouse; D051076:Proto-Oncogene Proteins c-fyn; D019061:src-Family Kinases; D064413:3-Phosphoinositide-Dependent Protein Kinases; C578562:PDPK1 protein, human; D017346:Protein Serine-Threonine Kinases