Different roles of proteolipids and 70-kDa subunits of V-ATPase in growth and death of cultured human cells

Background: The vacuolar-type proton-translocating adenosine triphosphatase (V-ATPase) plays important roles in cell growth and tumour progression. V-ATPase is composed of two distinct structures, a hydrophilic catalytic cytosolic sector (V-1 ) and a hydrophobic transmembrane sector (V-0 ). The V-1 sector is composed of 5-8 different subunits with the structure A(3) B-3 C-1 D-1 E-1 F-1 G(1) H-1 . The V-0 sector is composed of 5 different subunits with the structure 116(1) 38(1) 19(1) 16(6) . The over-expression of 16-kDa proteolipid subunit of V-ATPase in the perinuclear region of the human adventitial fibroblasts promotes phenotypic modulation that contributes to neointimal formation and medial thickening. A relationship between oncogenicity and the expression of the 16-kDa proteolipid has also been suggested in human pancreatic carcinoma tissue. Results: We found that the mRNA levels of the 16-kDa proteolipid but not of the 70-kDa subunit of V-ATPase in human myofibroblasts were more abundant in serum-containing medium (MF(+) cells) than serum-free medium (MF(-) cells). In HeLa cells, the levels of mRNA and protein of the 16-kDa, 21-kDa or 70-kDa were clearly suppressed when the corresponding anti-sense oligonucleotides were administered to the culture medium. The growth rate and viability (mostly due to necrosis) of HeLa cells were reduced markedly by the 16-kDa and 21-kDa anti-sense, but little by the 70-kDa anti-sense, and not at all by any sense oligonucleotides. The localization of 16-kDa/21-kDa proteolipid subunits was different from that of the 70-kDa subunit in HeLa cells. Conclusion: These results suggest that the 16-kDa and 21-kDa proteolipid subunits of the V-0 sector play crucial roles in growth and death of cultured human cells. Our results may provide new insights into the mechanism and therapeutic implications for vessel wall hyperplasia and tumorigenesis.