High impact information on Vha55

• As the ultimate target is the V-ATPase in the apical plasma membrane, this selective activation of mitochondria is clearly adaptive [1].
• The results highlight the dynamic nature and both spatial and temporal heterogeneity of calcium signaling possible in differentiated, organotypic cells and provide a new model for neuroendocrine control of V-ATPase [1].
• Analysis and inactivation of vha55, the gene encoding the vacuolar ATPase B-subunit in Drosophila melanogaster reveals a larval lethal phenotype [2].
• The P-element null allele of vha55 was shown also to suppress ectopic sex combs in Polycomb males, suggesting that transcriptional silencing may be modulated by genes other than those with known homeotic or DNA binding functions [2].
• The P-element vha55 insertion was shown to be allelic to a known lethal complementation group l(3)SzA (= l(3)87Ca) at 87C, for which many alleles have been described previously [2].

Biological context of Vha55

• Lethality of these alleles could be reverted by transformation of flies with a wild type vha55::GFP fusion, confirming that the lethal phenotype described for these alleles was due to defects in V-ATPase function [3].
• Here, mutations underlying five extant lethal alleles of vha55, encoding the B subunit, were identified, including a premature termination codon and two mutations very close to residues thought to participate in the catalytic site of the enzyme [3].
• A Drosophila melanogaster cDNA encoding vha55, the 55-kDa vacuolar ATPase (V-ATPase) regulatory B-subunit, was characterized and mapped to 87C2-4 on chromosome 3R [2].
• Involvement of V-ATPase in the regulation of cell size in the fly's visual system [4].
• The amino acid sequence (458 amino acids; Mr, 51,308) of B subunit of the M-12 enzyme was 74%, 53%, 52% and 54% identical with those of the ATPases from E. hirae, T. thermophilus, N. crassa and D. melanogaster, respectively [5].

Anatomical context of Vha55

• The transparent Malpighian tubule phenotype first identified in lethal alleles of vha55, the gene encoding the B-subunit, is shown to be general to those plasma membrane V-ATPase subunits for which lethal alleles are available, and to be caused by failure to accumulate uric acid crystals [6].
• Moreover, vacuolar-type H+-ATPase (V-ATPase) in the optic lobe is thought also to participate in such regulation [4].
• In the visual systems of both fly species V-ATPase was localized immunocytochemically to the compound eye photoreceptors [4].
• Intracellular pH regulation by the plasma membrane V-ATPase in Malpighian tubules of Drosophila larvae [7].
• The vacuolar H+-ATPase (V-ATPase) is a multisubunit enzyme that couples ATP hydrolysis to proton pumping across membranes [8].

Physical interactions of Vha55

• A consensus nuclear factor Y (NF-Y) element was able to specifically compete for formation of the novel complex, whereas antiserum directed against the B-subunit of NF-Y supershifted the complex without disturbing binding by the Sp3/Sp1 proteins [9].

Other interactions of Vha55

• The SzA mutations of the B subunit of the Drosophila vacuolar H+ ATPase identify conserved residues essential for function in fly and yeast [3].

References