InsP3-mediated intracellular calcium signalling is altered by expression of synaptojanin-1.
Phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] plays an important physiological role as a precursor for the InsP3-mediated intracellular calcium (Ca2+) signalling cascade. It also regulates membrane trafficking, actin function and transmembrane proteins. SJ-1 (synaptojanin-1), a phosphoinositide phosphatase, regulates the turnover of a PtdIns(4,5)P2 pool involved in clathrin and actin dynamics at the cell surface. We tested the interrelationship of this pool with PtdIns(4,5)P2 pools involved in Ca2+ signalling by expressing in Chinese-hamster ovary cells full-length SJ-1 or its 5-Pase (inositol 5-phosphatase) domain. SJ-1 significantly attenuated the generation of Ca2+ oscillations induced by ATP and the 5-Pase domain mimicked this effect. These changes correlated with increased PtdIns(4,5)P2 phosphatase activity of cellular extracts. Overexpression of the endoplasmic reticulum-anchored PtdIns(4)P phosphatase Sac1 did not affect Ca2+ oscillations, although it increased the Ca2+ efflux rate from intracellular stores. The ability of SJ-1 to alter intracellular Ca2+ signalling indicates a close functional interrelationship between plasma membrane PtdIns(4,5)P2 pools that control actin and endocytosis and those involved in the regulation of specific spatio-temporal Ca2+ signals.
Johenning
Friedrich W
FW
Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA.
Wenk
Markus R
MR
Uhlén
Per
P
Degray
Brenda
B
Lee
Eunkyung
E
De Camilli
Pietro
P
Ehrlich
Barbara E
BE
D000255:Adenosine Triphosphate / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D016466:CHO Cells / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D020134:Catalytic Domain / Q000502:physiology; D002460:Cell Line; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000201:enzymology; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D000072181:Inositol Polyphosphate 5-Phosphatases; D042541:Intracellular Space / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis; D009419:Nerve Tissue Proteins / Q000096:biosynthesis*; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000096:biosynthesis* / Q000378:metabolism
D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; C416669:Sac1 protein, mammalian; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; C097702:synaptojanin; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; D002118:Calcium