Sphingosine Kinase Type 1 Interacting Protein (SKIP)

SKIP interacted with SPHK1. Overexpression of SKIP in HEK293 cells significantly reduced SPHK1 activity in both the cytosolic and particulate fractions. Using BrdU incorporation, they showed that NIH3T3 cells expressing SPHK1 displayed an increased proportion of cells in S phase; however, SKIP overexpression reduced BrdU incorporation and abolished SPHK1-promoted cell proliferation. In addition, SKIP overexpression enhanced apoptosis of serum-starved cells and induced cell rounding, and SKIP reduced activation of ERK1 (MAPK3)/ERK2 (MAPK1) induced by SPHK1.The deduced 305-amino acid protein shared 99% identity with the C terminus of KIAA1678. Northern blot analysis of human tissues detected a 7-kb transcript with highest expression in heart, followed by spleen, ovary, and brain.