The spatial distribution of inositol 1,4,5-trisphosphate receptor isoforms shapes Ca2+ waves.
Cytosolic Ca(2+) is a versatile second messenger that can regulate multiple cellular processes simultaneously. This is accomplished in part through Ca(2+) waves and other spatial patterns of Ca(2+) signals. To investigate the mechanism responsible for the formation of Ca(2+) waves, we examined the role of inositol 1,4,5-trisphosphate receptor (InsP3R) isoforms in Ca(2+) wave formation. Ca(2+) signals were examined in hepatocytes, which express the type I and II InsP3R in a polarized fashion, and in AR4-2J cells, a nonpolarized cell line that expresses type I and II InsP3R in a ratio similar to what is found in hepatocytes but homogeneously throughout the cell. Expression of type I or II InsP3R was selectively suppressed by isoform-specific DNA antisense in an adenoviral delivery system, which was delivered to AR4-2J cells in culture and to hepatocytes in vivo. Loss of either isoform inhibited Ca(2+) signals to a similar extent in AR4-2J cells. In contrast, loss of the basolateral type I InsP3R decreased the sensitivity of hepatocytes to vasopressin but had little effect on the initiation or spread of Ca(2+) waves across hepatocytes. Loss of the apical type II isoform caused an even greater decrease in the sensitivity of hepatocytes to vasopressin and resulted in Ca(2+) waves that were much slower and delayed in onset. These findings provide evidence that the apical concentration of type II InsP3Rs is essential for the formation of Ca(2+) waves in hepatocytes. The subcellular distribution of InsP3R isoforms may critically determine the repertoire of spatial patterns of Ca(2+) signals.
Hernandez
Erick
E
Department of Pediatrics, Yale University, New Haven, Connecticut 06520.
Leite
M Fatima
MF
Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil.
Guerra
Mateus T
MT
Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil.
Kruglov
Emma A
EA
Department of Medicine, Yale University, New Haven, Connecticut 06520.
Bruna-Romero
Oscar
O
Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil.
Rodrigues
Michele A
MA
Department of Physiology and Biophysics, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil; Department of Medicine, Yale University, New Haven, Connecticut 06520.
Gomes
Dawidson A
DA
Department of Medicine, Yale University, New Haven, Connecticut 06520.
Giordano
Frank J
FJ
Department of Medicine, Yale University, New Haven, Connecticut 06520.
Dranoff
Jonathan A
JA
Department of Medicine, Yale University, New Haven, Connecticut 06520.
Nathanson
Michael H
MH
Department of Medicine, Yale University, New Haven, Connecticut 06520. Electronic address: michael.nathanson@yale.edu.
D000818:Animals; D001483:Base Sequence; D015220:Calcium Channels / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D022781:Hepatocytes / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000737:chemistry / Q000502:physiology; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D014667:Vasopressins / Q000502:physiology
D015220:Calcium Channels; C506928:ITPR2 protein, rat; D053496:Inositol 1,4,5-Trisphosphate Receptors; C488910:Itpr1 protein, rat; D008562:Membrane Glycoproteins; D020033:Protein Isoforms; D018160:Receptors, Cytoplasmic and Nuclear; D014667:Vasopressins