The Drosophila Ral GTPase regulates developmental cell shape changes through the Jun NH(2)-terminal kinase pathway.
The Ral GTPase is activated by RalGDS, which is one of the effector proteins for Ras. Previous studies have suggested that Ral might function to regulate the cytoskeleton; however, its in vivo function is unknown. We have identified a Drosophila homologue of Ral that is widely expressed during embryogenesis and imaginal disc development. Two mutant Drosophila Ral (DRal) proteins, DRal(G20V) and DRal(S25N), were generated and analyzed for nucleotide binding and GTPase activity. The biochemical analyses demonstrated that DRal(G20V) and DRal(S25N) act as constitutively active and dominant negative mutants, respectively. Overexpression of the wild-type DRal did not cause any visible phenotype, whereas DRal(G20V) and DRal(S25N) mutants caused defects in the development of various tissues including the cuticular surface, which is covered by parallel arrays of polarized structures such as hairs and sensory bristles. The dominant negative DRal protein caused defects in the development of hairs and bristles. These phenotypes were genetically suppressed by loss of function mutations of hemipterous and basket, encoding Drosophila Jun NH(2)-terminal kinase kinase (JNKK) and Jun NH(2)-terminal kinase (JNK), respectively. Expression of the constitutively active DRal protein caused defects in the process of dorsal closure during embryogenesis and inhibited the phosphorylation of JNK in cultured S2 cells. These results indicate that DRal regulates developmental cell shape changes through the JNK pathway.
Sawamoto
K
K
Division of Neuroanatomy, Department of Neuroscience, Biomedical Research Center, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan.
Winge
P
P
Koyama
S
S
Hirota
Y
Y
Yamada
C
C
Miyao
S
S
Yoshikawa
S
S
Jin
M H
MH
Kikuchi
A
A
Okano
H
H
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D048429:Cell Size; D003001:Cloning, Molecular; D004331:Drosophila melanogaster / Q000166:cytology* / Q000196:embryology* / Q000201:enzymology / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D047108:Embryonic Development; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect / Q000235:genetics / Q000502:physiology; D017403:In Situ Hybridization; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D010641:Phenotype; D010766:Phosphorylation; D012679:Sense Organs / Q000196:embryology / Q000254:growth & development / Q000648:ultrastructure; D015398:Signal Transduction; D014921:Wings, Animal / Q000196:embryology / Q000254:growth & development / Q000648:ultrastructure; D020725:ral GTP-Binding Proteins
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020725:ral GTP-Binding Proteins