Regulation of Protein 4.1-Membrane Associations by a Phosphoinositide

Mechanism(s) underlying activation of store-operated Ca2+ entry currents, ISOC, remain incompletely understood. F-actin configuration is an important determinant of channel function, although the nature of interaction between the cytoskeleton and ISOC channels is unknown. We examined whether the spectrin membrane skeleton couples Ca2+ store depletion to Ca2+ entry. Thapsigargin activated an endothelial cell ISOC (−45 pA at −80 mV) that reversed at +40 mV, was inwardly rectifying when Ca2+ was the charge carrier, and was inhibited by La3+ (50 μM). Disruption of the spectrin–protein 4.1 interaction at residues A207-V445 of βSpIIΣ1 decreased the thapsigargin-induced global cytosolic Ca2+ response by 50% and selectively abolished the endothelial cell ISOC, without altering activation of a nonselective current through cyclic nucleotide–gated channels. In contrast, disruption of the spectrin–actin interaction at residues A47-K186 of βSpIIΣ1 did not decrease the thapsigargin-induced global cytosolic Ca2+ response or inhibit ISOC. Results indicate that the spectrin–protein 4.1 interaction selectively controls ISOC, indicating that physical coupling between calcium release and calcium entry is reliant upon the spectrin membrane skeleton.

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Characterization of a cDNA encoding a novel band 4.1-like protein in zebrafish

Biochemistry and Cell Biology ◽

10.1139/o97-078 ◽

1997 ◽

Vol 75 (5) ◽

pp. 623-632 ◽

Cited By ~ 8

Author(s):

Gregory M Kelly ◽

Bruno Reversade

Keyword(s):

Cell Communication ◽

Membrane Skeleton ◽

Adult Brain ◽

Dependent Manner ◽

Midblastula Transition ◽

Protein 4.1 ◽

Calcium Dependent ◽

Calcium Calmodulin Dependent ◽

Integral Role

Membrane skeleton protein 4.1 and other members of a family of proteins that link the cytoskeleton to the plasma membrane may play an integral role in cell communication during development. The polymerase chain reaction and degenerate oligodeoxynucleotide primers to consensus sequences in the putative membrane-binding domain of the protein 4.1 superfamily were used to isolate cDNAs encoding members of the zebrafish protein 4.1 family. Zebrafish stage- and tissue-specific first strand cDNA was used in the PCR. After the reaction, amplicons of the predicted size were sequenced to confirm their relationship to the protein 4.1 superfamily. One cDNA, with a high degree of similarity to a mouse novel band 4.1-like cDNA, was used to probe a zebrafish adult brain library. A 2.4-kb cDNA was isolated and found to encode a 619 amino acid polypeptide homologous to mouse novel band 4.1-like protein 4. Zebrafish nbl4 mRNA is maternally supplied and is expressed throughout embryogenesis. In adults, nbl4 is found in the ovary, eye, heart, and brain, but not in gut or skeletal muscle. When synthetic nbl4 mRNA is translated in vitro it binds calmodulin in a calcium-dependent manner. These data indicate that zebrafish nbl4 is a maternal transcript owing to its presence before the midblastula transition, and it is present later on in specific adult structures. The ability to bind calmodulin would suggest that the function of nbl4 protein may be potentially regulated via a calcium-calmodulin dependent mechanism.

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