Calcium- and polyphosphate-containing acidic granules of sea urchin eggs are similar to acidocalcisomes, but are not the targets for NAADP
Year: 2010
Type: article
Abstract: Acidocalcisomes are acidic calcium-storage compartments described from bacteria to humans and characterized by their high content in poly P (polyphosphate), a linear polymer of many tens to hundreds of Pi residues linked by high-energy phosphoanhydride bonds. In the present paper we report that millimolar levels of short-chain poly P (in terms of Pi residues) and inorganic PPi are present in sea urchin extracts as detected using 31P-NMR, enzymatic determinations and agarose gel electrophoresis. Poly P was localized to granules randomly distributed in the sea urchin eggs, as shown by labelling with the poly-P-binding domain of Escherichia coli exopolyphosphatase. These granules were enriched using iodixanol centrifugation and shown to be acidic and to contain poly P, as determined by Acridine Orange and DAPI (4',6'-diamidino-2-phenylindole) staining respectively. These granules also contained large amounts of calcium, sodium, magnesium, potassium and zinc, as detected by X-ray microanalysis, and bafilomycin A1-sensitive ATPase, pyrophosphatase and exopolyphosphatase activities, as well as Ca2+/H+ and Na+/H+ exchange activities, being therefore similar to acidocalcisomes described in other organisms. Calcium release from these granules induced by nigericin was associated with poly P hydrolysis. Although NAADP (nicotinic acid-adenine dinucleotide phosphate) released calcium from the granule fraction, this activity was not significantly enriched as compared with the NAADP-stimulated calcium release from homogenates and was not accompanied by poly P hydrolysis. GPN (glycyl-L-phenylalanine-naphthylamide) released calcium when added to sea urchin homogenates, but was unable to release calcium from acidocalcisome-enriched fractions, suggesting that these acidic stores are not the targets for NAADP.
Source: Biochemical Journal
DOI: 10.1042/bj20091956
Institutions: Universidade Federal do Rio de Janeiro, University of Georgia, National Institute of Science and Technology for Structural Biology and Bioimaging, Instituto de Biofísica Carlos Chagas Filho, Instituto Nacional de Metrologia, Qualidade e Tecnologia, University of Illinois Urbana-Champaign
Language: English
Subfield: Physiology
Domain: Life Sciences
SDG: Life below water
Open Access status: hybrid
Funders: Ellison Medical Foundation, Georgia Research Alliance, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, National Institutes of Health, National Institute of General Medical Sciences, National Institute of Allergy and Infectious Diseases
OpenAlex ID: W2161864020