Extended longevity mutants are extremely useful to understand the molecular mechanism of longevity determination. Here we report identification and characterization of the Drosophila Plenty of SH3s (DPOSH) gene, a candidate that might be associated with the extended longevity phenotype. DPOSH encodes a protein containing a RING finger domain and four SH3 domains. We showed that neural-specific overexpression of DPOSH could extend the mean longevity of adult flies by 14% at 25 degrees C without affecting viability or morphology. In contrast, forced expression of DPOSH in developing imaginal discs produced various phenotypes including lethality and morphological defects such as loss of crossvein, notched wing, and disordered hair polarity. Puckered, a target gene of JNK/SAPK pathway, was activated by overexpression of DPOSH and the forced expression phenotypes were suppressed by introducing a mutation of Drosophila JNK (bsk) or JNKK (hep), suggesting that the JNK/SAPK signaling pathway is one of the critical elements in the determination of longevity.