Effect of calcium ions on human calcitonin. Possible implications for bone resorption by osteoclasts.

Calcium ions (Ca(2+)) are indispensable for life and are involved in important physiological actions, which makes maintaining a constant level of blood Ca(2+) essential. Ca(2+) is mainly stored in bones which serve as a reservoir and its homeostasis is modulated by various hormones. Human calcitonin (hCt) is a small peptide hormone that exerts its physiological effect on Ca(2+) metabolism by means of osteoclast-mediated bone resorption inhibition.

Acetyl-[Asn30,Tyr32]-calcitonin fragment 8-32 forms channels in phospholipid planar lipid membranes.

The N-terminally truncated derivative of salmon calcitonin (sCt) (acetyl-[Asn(30),Tyr(32)]-calcitonin fragment 8-32) (AC 187) lacks hormonal activity and is a potent and selective antagonist of the hormone and amylin receptor. It was investigated for its capability to interact and form channels in palmitoleoylphosphatidylcholine:dioleoylphosphatidylglycerol planar lipid membranes. Interestingly, AC 187 exhibits channel activity, whose parameters, i.

Effect of pH-variation on insertion and ion channel formation of human calcitonin into planar lipid bilayers.

Human calcitonin is the physiological hormone involved in calcium-phosphorus homeostasis. However, its use is limited by its propensity to form aggregates. We find that the type of host lipid has a pronounced influence on human calcitonin fibrillation or incorporation, as assessed by channel formation, in planar lipid membranes at neutral pH.

Effect of nanomolar concentrations of sodium dodecyl sulfate, a catalytic inductor of alpha-helices, on human calcitonin incorporation and channel formation in planar lipid membranes.

Human Calcitonin (hCt) is a peptide hormone which has a regulatory action in calcium-phosphorus metabolism. It is currently used as a therapeutic tool in bone pathologies such as osteoporosis and Paget's disease. However, due to its amphiphilic property tends to form a gelatinous solution in water which consists of fibrils that limits its therapeutic use.

Effect of sterols on beta-amyloid peptide (AbetaP 1-40) channel formation and their properties in planar lipid membranes.

We investigate the role played by membrane composition on the interaction and self-assembly of beta-amyloid peptide (AbetaP1-40) during pore formation in planar lipid membranes (PLMs). Incorporation studies showed that AbetaP does not interact with zwitterionic membranes made up of phosphatidylcholine, whereas the addition of cholesterol or ergosterol to the membranes leads to channel formation. Among the PLMs used, a higher propensity of AbetaP to form channels at low applied potential (+/-20 mV) was observed in 7-dehydrocholesterol and in oxidized cholesterol PLMs.

Magainin 2 channel formation in planar lipid membranes: the role of lipid polar groups and ergosterol.

Magainin 2, a polycationic peptide, displays bactericidal and tumoricidal activity, presumably interacting with negatively charged phospholipids in the membrane hosts. In this work, we investigate the role played by the lipid head-group in the interactions and self-association of magainin 2 during pore formation in lipid bilayers. Two methods are used: single-channel and macroscopic incorporation into planar lipid membranes.

Mitochondrial porin incorporation into black lipid membranes: ionic and gating contribution to the total current.

We present a new ac device useful for simultaneous measurements of ionic charge movement (conductance) and gating charge displacement (capacitance) in mitochondrial porin channels incorporated in two kinds of black lipid membranes (BLMs), made up of phosphatidylinositol (charged surface) and oxidized cholesterol (neutral surface). In particular, we investigated the conductance/capacitance variations during the process of porin incorporation (VDAC) at different porin concentrations. While conductance variations are present throughout the porin concentration range investigated, a threshold value seems to be necessary in order to detect a significant capacitance variation.