Immunolocalization of Na,K-ATPase in blowfly photoreceptor cells

Abstract

The Na,K-ATPase (sodium pump) plays a central role in the physiology of arthropod photoreceptors as it re-establishes gradients for Na+ and K+ after light stimulation. We have mapped the distribution of the Na,K-ATPase in the photoreceptors of the blowfly (Calliphora erythrocephala) by immunofluorescent and immunogold cytochemistry, and demonstrate that the distribution pattern is more complex than previously presumed. High levels of sodium pumps have been detected consistently in all photoreceptors R1-8 on the nonreceptive surface, but no sodium pumps are found on the microvillar rhabdomere. Within the nonreceptive surface of the cells R1-6, however, the sodium pumps are confined to sites juxtaposed to neighboring photoreceptor or glial cells; no sodium pumps have been detected on the parts of the nonreceptive surface exposed to the intra-ommatidial space. In R7 and R8, the sodium pumps are found over the entire nonreceptive surface. The cytoskeletal protein spectrin colocalizes with the sodium pumps suggesting that linkage of the pump molecules to the spectrin-based submembrane cytoskeleton contributes to the maintenance of the complex pattern of pump distribution.

Insect retinal pigments: Spectral characteristics and physiological functions

“…The main ATP consumer is the sodium pump in the plasma membrane, which evid- ently has to work continuously to maintain considerable sodium and potassium gradients. Sensibly, the sodium pump molecules are local-ized in the non-rhabdomeric part of the photoreceptor membrane, as shown in blowfly by immunofluorescence and immunogold cytochemistry (Baumann et al, 1994). In addition, the mitochondria tend to concentrate near their customers in the cell boundary (see Fig.…”

Immunolocalization of Na + , K + -ATPase in the gill epithelium of rainbow trout, Oncorhynchus mykiss

“…The α subunit is highly conserved in evolution as illustrated by the analysis of the amino acid sequence in Drosophila melanogaster, a sequence that is about 80% similar to the vertebrate sequence (Lebovitz et al 1989), there being approximately 90% similarity between birds, fish, and mammals (Schull et al 1985;Kawakami et al 1985;Takeyasu et al 1988). The monoclonal antibody IgG α5, which has been raised against the catalytic α subunit of chicken Na + ,K + -ATPase, recognizes three α isoforms (α1, α2, α3) and cross-reacts with the α subunits of Na + ,K + -ATPases of several invertebrate epithelia (Lebovitz et al 1989;Baumann et al 1994;Just and Walz 1994).…”

“…Fambrough) binds specifically to the cytosolic epitope and recognizes all three isoforms (α1, α2, α3) of the α subunit of the Na + ,K + -ATPase in vertebrates Kone et al 1991). It has also been shown to cross-react with the α subunit of invertebrate epithelia (Drosophila melanogaster: Lebovitz et al 1989; Apis mellifera: Bauman and Takeyasu 1993; Calliphora erythrocephala: Baumann et al 1994;Periplaneta americana: Just and Walz 1994). The antibody can be obtained from the Developmental Studies Hybridoma Bank, which is maintained by the Department of Pharmacology and Molecular Sciences, John Hopkins, University School for Medicine, Baltimore and the Department of Biological Sciences, University of Iowa, Iowa City (contract N°1-HD-2-3144, MICHD).…”

“…The α subunit is the catalytic part of the sodium pump and shows a highly conserved amino acid sequence in diverse vertebrate (mammals: Shull et al 1985;birds: Takeyasu et al 1988, fish: Kawakami et al 1985 and invertebrate (insects: Lebovitz et al 1989) species. The monoclonal antibody α5, raised against the catalytic α subunit of the avian sodium pump (Takeyasu et al 1988) has been selected for this study of fish gill epithelial cells, because of the likelihood of species cross-reactivity, as shown in recent studies with insects (Just and Walz 1994;Baumann et al 1994).…”

Immunocytochemical Localization of Na+,K+-ATPase in the Calcium-transporting Sternal Epithelium of the Terrestrial Isopod Porcellio scaber L. (Crustacea)

“…This antibody binds specifically to all three known ␣-subunits (␣ 1 -␣ 3 ). Crossreactivity with the ␣-subunit of epithelia in insects includes Drosophila melanogaster (Lebovitz et al 1989), Apis mellifera (Baumann and Takeyasu 1993), Calliphora erythrocephala (Baumann et al 1994), Periplaneta americana (Just and Walz 1994), and vertebrates: Oncorhynchus mykiss (Witters et al 1996).…”