Properties of membranous phospholipase C from WRK1 cell: sensitivity to guanylnucleotides and bacterial toxins.
As previously described, WRK1 plasma membrane possesses a vasopressin-sensitive phospholipase C [G. Guillon et al., 1986, FEBS Lett. 196, 155-159]. In the present study, we examined the sensitivity of this enzyme to guanylnucleotides. GTP gamma S induces a time- and dose-dependent stimulation of Ins(1,4,5)P3 and Ins(1,4)P2 accumulation. No accumulation of InsP1, Ins(1,3,4)P3 or Ins(1,3,4,5)P4 occurred under similar conditions. Gpp(NH)p produced the same effect but was less potent. GTP and a nonhydrolyzable analogue of ATP, App(NH)p, were without effect. Calcium also stimulated the phospholipase C activity in a time- and dose-dependent manner. In the absence of calcium, the activity of GTP gamma S was considerably reduced. Physiological calcium concentrations (between 10(-8) and 10(-7) M), allowed maximal GTP gamma S stimulation of phospholipase C activity. In this system, the presence of vasopressin alone did not generate inositol phosphate accumulation. However, this hormone: (i) reduced the lag-time observed during GTP gamma S stimulation, (ii) increased the sensitivity of phospholipase C to GTP and to GTP gamma S, and (iii) did not modify the stimulation of phospholipase C induced by maximal doses of GTP gamma S. Unlike sodium fluoride, GTP gamma S elicited an irreversible activation of phospholipase C. Calcium, GTP gamma S and sodium fluoride stimulated the phospholipase C activity via mechanisms sharing a common step, since their maximal effects were not additive. Cholera toxin treatment, known to produce complete ADP-ribosylation of 'alpha s' subunits, partially reduced the basal and the maximal GTP gamma S-mediated stimulation of phospholipase C activity as well as that caused by vasopressin. This inhibition was not mimicked by treatment with either forskolin or pertussis toxin.
Guillon
G
G
Centre CNRS-INSERM de Pharmacologie-Endocrinologie, Montpellier, France.
Mouillac
B
B
Berrada
R
R
Balestre
M N
MN
Lombard
C
C
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D002118:Calcium / Q000502:physiology; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D037342:Pertussis Toxin; D011945:Receptors, Angiotensin / Q000502:physiology*; D017483:Receptors, Vasopressin; D013873:Thionucleotides / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism*; D014667:Vasopressins / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D007295:Inositol Phosphates; D011945:Receptors, Angiotensin; D017483:Receptors, Vasopressin; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D014667:Vasopressins; D000246:Adenosine Diphosphate Ribose; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D002772:Cholera Toxin; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D002118:Calcium