Otoconin-22, the major protein of aragonitic frog otoconia, is a homolog of phospholipase A2

Pote, Kenneth G.; Hauer, Christoph; Michel, Hanspeter; Shabanowitz, Jeffrey; Hunt, Donald F.; Kretsinger, Robert H.

doi:10.1021/bi00070a007

Cited by 61 publications

(44 citation statements)

References 24 publications

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“…To remove the calcium carbonate from the ELS, we treated the latter with 10% ethyenediamine-N,N,N,N'-tetraacetatic acid (EDTA) in water at 4°C for 3 days according to the method of Pote et al (1993). These samples were homogenized in cell lysis buffer (50 mM Tris-HCl, pH 8.0, 0.15 M NaCl, 1% Triton X-100, 0.1 mg/ml PMSF, 1 μg/ml aprotinin) and centrifuged in a microcentrifuge for 10 min to remove insoluble material.…”

Section: Western Blot Analysismentioning

confidence: 99%

Cloning and Expression of Vacuolar Proton-Pumping ATPase Subunits in the Follicular Epithelium of the Bullfrog Endolymphatic Sac

et al. 2007

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In an investigation aimed at clarifying the mechanism of crystal dissolution of the calcium carbonate lattice in otoconia (the mineral particles embedded in the otolithic membrane) of the endolymphatic sac (ELS) of the bullfrog, cDNAs encoding the A-and E-subunits of bullfrog vacuolar protonpumping ATPase (V-ATPase) were cloned and sequenced. The cDNA of the A-subunit consisted of an 11-bp 5'-untranslated region (UTR), a 1,854-bp open reading frame (ORF) encoding a protein comprising 617 amino acids with a calculated molecular mass of 68,168 Da, and a 248-bp 3'-UTR followed by a poly(A) tail. The cDNA of the E-subunit consisted of a 72-bp 5'-UTR, a 681-bp ORF encoding a protein of 226 amino acids with a calculated molecular mass of 26,020 Da, and a 799-bp 3'-UTR followed by a poly(A) tail. Western blot and immunofluorescence analyses using specific anti-peptide antisera against the V-ATPase A-and E-subunits revealed that these subunits were present in the ELS, urinary bladder, skin, testes, and kidneys. In the ELS, positive cells were scattered in the follicular epithelium which, as revealed by electron microscopy, corresponds to the location of mitochondria-rich cells. These findings suggest that V-ATPase, including the A-and Esubunits, exists in mitochondria-rich cells of the ELS, which might be involved in dissolution of the calcium carbonate crystals in the lumen of the ELS.

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Section: Western Blot Analysismentioning

confidence: 99%

Cloning and Expression of Vacuolar Proton-Pumping ATPase Subunits in the Follicular Epithelium of the Bullfrog Endolymphatic Sac

et al. 2007

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“…Each complement amounts to up to two dozen different proteins, as determined by gel electrophoresis (Pote et al 1993;Wang et al 1998 ;Verpy et al 1999;Murayama et al 2000Murayama et al , 2002this manuscript). Only five proteins have been located in otoliths or otoconia as well as functionally characterized.…”

Section: Introductionmentioning

confidence: 99%

“…Only five proteins have been located in otoliths or otoconia as well as functionally characterized. First, otoconin 90, the major otoconia protein, in mouse (Wang et al 1998;Verpy et al 1999;Zhao et al 2007) and zebrafish (Petko et al 2008), and its homolog otoconin 22 in frog (Pote et al 1993;Yaoi et al 2004). Second, otolith matrix protein-1, the major otolith protein, in trout and zebrafish (Murayama et al 2000(Murayama et al , 2004(Murayama et al , 2005.…”

Section: Introductionmentioning

confidence: 99%

Sparc Protein Is Required for Normal Growth of Zebrafish Otoliths

Kang

Stevenson

Yau

et al. 2008

JARO

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Otoliths and the homologous otoconia in the inner ear are essential for balance. Their morphogenesis is less understood than that of other biominerals, such as bone, and only a small number of their constituent proteins have been characterized. As a novel approach to identify unknown otolith proteins, we employed shotgun proteomics to analyze crude extracts from trout and catfish otoliths. We found three proteins that had not been associated previously with otolith or otoconia formation: 'Secreted acidic cysteine rich glycoprotein' (Sparc), an important bone protein that binds collagen and Ca 2+ ; precerebellin-like protein, which contains a C1q domain and may associate with the collagenous otolin-1 during its assembly into a framework; and neuroserpin, a serine protease inhibitor that may regulate local protease activity during framework assembly. We then used the zebrafish to investigate whether Sparc plays a role in otolith morphogenesis. Immunodetection demonstrated that Sparc is a true constituent of otoliths. Knockdown of Sparc expression in morphant zebrafish resulted in four principal types of defective otoliths: smaller, extra and ectopic, missing and fused, or completely absent. Smaller size was the predominant phenotype and independent of the severity of oticvesicle defects. These results suggested that Sparc is directly required for normal otolith growth.

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“…Oc90 is characterized by a high abundance of negatively charged amino acid residues and has two regions of homology with secretory phospholipase A2 (PLA2) (10). The PLA2 domain lacks enzymatic activity but retains calcium binding function (11). It has been proposed that Oc90 is responsible for determining the calcium carbonate polymorph type of otoconia, namely calcite (12).…”

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confidence: 99%

Calcium Oxalate Stone Formation in the Inner Ear as a Result of an Slc26a4 Mutation

Dror

Politi

Shahin

et al. 2010

Journal of Biological Chemistry

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Calcium oxalate stone formation occurs under pathological conditions and accounts for more than 80% of all types of kidney stones. In the current study, we show for the first time that calcium oxalate stones are formed in the mouse inner ear of a genetic model for hearing loss and vestibular dysfunction in humans. The vestibular system within the inner ear is dependent on extracellular tiny calcium carbonate minerals for proper function. Thousands of these biominerals, known as otoconia, are associated with the utricle and saccule sensory maculae and are vital for mechanical stimulation of the sensory hair cells. We show that a missense mutation within the Slc26a4 gene abolishes the transport activity of its encoded protein, pendrin. As a consequence, dramatic changes in mineral composition, size, and shape occur within the utricle and saccule in a differential manner. Although abnormal giant carbonate minerals reside in the utricle at all ages, in the saccule, a gradual change in mineral composition leads to a formation of calcium oxalate in adult mice. By combining imaging and spectroscopy tools, we determined the profile of mineral composition and morphology at different time points. We propose a novel mechanism for the accumulation and aggregation of oxalate crystals in the inner ear.Biomineralization processes in the human body normally occur in a variety of different tissues, including bones, teeth, and otoconia within the vestibular system of the inner ear. The vestibular system is comprised of five sensory organs. Three cristae connected to semicircular canals are sensitive for angular movement, and the saccule and utricle are sensitive for linear acceleration and gravity. Otoconia are small highly dense calcitic minerals that associate exclusively with the saccule and utricle. Thousands of otoconia, partially embedded in a gelatinous matrix, are supported on the sensory epithelium and serve as an inertial mass that is critical for mechanical stimulation (1, 2) Movement of the otoconial layer through action of gravitational or inertial forces activate the underlying mechanosensory hair cells to generate action potentials that are transmitted to the brain.The biomineralization process, such as in otoconia formation, involves organic and inorganic components and results in biominerals that differ significantly in morphology and mechanical properties from similar synthetic or geological minerals (3, 4). Otoconia formation occurs outside the cells and therefore depends on secretion of the required assembly components into the endolymphatic spaces (5). Otoconia seeding in mice begins as early as embryonic day (E)14.5 4 and initiates extensive mineral growth, with the highest rate of calcification at E15-16 (6). By postnatal day (P)7, otoconia achieve their final size and are maintained at progressive ages with a low rate of calcium turnover (7). The main inorganic fraction of otoconia in birds and mammals is calcite (CaCO 3 ), a polymorph of calcium carbonate (2,8). The organic fraction of otoconia contains s...

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Otoconin-22, the major protein of aragonitic frog otoconia, is a homolog of phospholipase A2

Cited by 61 publications

References 24 publications

Cloning and Expression of Vacuolar Proton-Pumping ATPase Subunits in the Follicular Epithelium of the Bullfrog Endolymphatic Sac

Cloning and Expression of Vacuolar Proton-Pumping ATPase Subunits in the Follicular Epithelium of the Bullfrog Endolymphatic Sac

Sparc Protein Is Required for Normal Growth of Zebrafish Otoliths

Calcium Oxalate Stone Formation in the Inner Ear as a Result of an Slc26a4 Mutation

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