Effects of profilin-annexin I association on some properties of both profilin and annexin I: modification of the inhibitory activity of profilin on actin polymerization and inhibition of the self-association of annexin I and its interactions with liposomes.
We have previously shown that annexin I, a member of a family of calcium-dependent phospholipid and membrane binding proteins, interacts with profilin with high specificity and affinity. This finding further suggests that annexin I is involved through profilin in the regulation of membrane-cytoskeleton organization. We have investigated the consequences of a complex formed by these two proteins on the functions of both profilin and annexin I. Annexin I is able to modify the inhibitory effect of profilin on actin polymerization. This action is partial and the mechanism involved appears to be complex. On the other hand, the association between annexin I and profilin is sufficiently strong to inhibit the self-association of annexin I. The binding capacity of annexin I to liposomes containing phosphatidylserine, which mimics annexin I binding to membranes, is also decreased by profilin. This binding is nevertheless restored when phosphatidylinositol 4,5-biphosphate (PtdInsP2) is included in the liposomes. Finally, the capacity of annexin I to aggregate liposomes is also modified. It is worthwhile mentioning that the liposomes-binding and liposomes-aggregating activities of annexin I are independently regulated. The cell localization and functions of annexin I and profilin suggest that interaction between these two proteins may be directly implicated in the regulation of membrane-cytoskeleton. The phospholipid composition of membranes may be one of the modulating factors.
Alvarez-Martinez
M T
MT
Institut National de la Santé et de la Recherche Médicale INSERM U431, Université de Montpellier II, France.
Porte
F
F
Liautard
J P
JP
Sri Widada
J
J
D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D017305:Annexin A1 / Q000737:chemistry / Q000378:metabolism*; D003285:Contractile Proteins; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism*; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates; D010718:Phosphatidylserines; D011108:Polymers; D051304:Profilins; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
D000199:Actins; D017305:Annexin A1; D003285:Contractile Proteins; D008081:Liposomes; D008840:Microfilament Proteins; C495738:PFN1 protein, human; D018129:Phosphatidylinositol Phosphates; D010718:Phosphatidylserines; D011108:Polymers; D051304:Profilins; D011994:Recombinant Proteins