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Application of circuit simulation method for differential modeling of TIM-2 iron uptake and metabolism in mouse kidney cells.

Xie Z, Harrison SH, Torti SV, Torti FM, Han J - Front Physiol (2013)

Bottom Line: At the end of endocytosis, about 28% HFt remained intact and the rest was degraded.Iron released from degraded HFt was in the labile iron pool (LIP) and stimulated the generation of endogenous HFt for new storage.Both experimental data and the model showed that TIM-2 was not involved in the process of iron export.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, North Carolina Agricultural and Technical State University Greensboro, NC, USA.

ABSTRACT
Circuit simulation is a powerful methodology to generate differential mathematical models. Due to its highly accurate modeling capability, circuit simulation can be used to investigate interactions between the parts and processes of a cellular system. Circuit simulation has become a core technology for the field of electrical engineering, but its application in biology has not yet been fully realized. As a case study for evaluating the more advanced features of a circuit simulation tool called Advanced Design System (ADS), we collected and modeled laboratory data for iron metabolism in mouse kidney cells for a H ferritin (HFt) receptor, T cell immunoglobulin and mucin domain-2 (TIM-2). The internal controlling parameters of TIM-2 associated iron metabolism were extracted and the ratios of iron movement among cellular compartments were quantified by ADS. The differential model processed by circuit simulation demonstrated a capability to identify variables and predict outcomes that could not be readily measured by in vitro experiments. For example, an initial rate of uptake of iron-loaded HFt (Fe-HFt) was 2.17 pmol per million cells. TIM-2 binding probability with Fe-HFt was 16.6%. An average of 8.5 min was required for the complex of TIM-2 and Fe-HFt to form an endosome. The endosome containing HFt lasted roughly 2 h. At the end of endocytosis, about 28% HFt remained intact and the rest was degraded. Iron released from degraded HFt was in the labile iron pool (LIP) and stimulated the generation of endogenous HFt for new storage. Both experimental data and the model showed that TIM-2 was not involved in the process of iron export. The extracted internal controlling parameters successfully captured the complexity of TIM-2 pathway and the use of circuit simulation-based modeling across a wider range of cellular systems is the next step for validating the significance and utility of this method.

No MeSH data available.


Comparison of iron storage rates between laboratory data and simulation. Cells were treated with biotinylated HFt loaded with 55Fe for various time points and the 55Fe amounts in biotinylated and non-biotinylated fractions were counted. Data shown are means and standard deviations for triplicate replication of the experiment. The experiment was performed in triplicate.
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Figure 6: Comparison of iron storage rates between laboratory data and simulation. Cells were treated with biotinylated HFt loaded with 55Fe for various time points and the 55Fe amounts in biotinylated and non-biotinylated fractions were counted. Data shown are means and standard deviations for triplicate replication of the experiment. The experiment was performed in triplicate.

Mentions: Degradation of biotinylated ferritin consisted of two phases with different degradation time constants (Figure 6). Phase one was for the first 4 h and phase two was for the remaining experimental period. In phases one and two, the concentration of biotinylated ferritin decreased with rates of about 20% per h and 1–2% per h, respectively. Possibly because biotinylated ferritin stayed within endosomes for approximately 2 h within phase one, it decreased faster due to the lower pH of endosome, which facilitates the ferritin degradation process in phase one. This indicates that not all of the exogenous ferritin degrades at the end of endosome (within the 2 h period) and the remaining ferritin continues degrading at a slower rate in the intracellular environment.


Application of circuit simulation method for differential modeling of TIM-2 iron uptake and metabolism in mouse kidney cells.

Xie Z, Harrison SH, Torti SV, Torti FM, Han J - Front Physiol (2013)

Comparison of iron storage rates between laboratory data and simulation. Cells were treated with biotinylated HFt loaded with 55Fe for various time points and the 55Fe amounts in biotinylated and non-biotinylated fractions were counted. Data shown are means and standard deviations for triplicate replication of the experiment. The experiment was performed in triplicate.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3675319&req=5

Figure 6: Comparison of iron storage rates between laboratory data and simulation. Cells were treated with biotinylated HFt loaded with 55Fe for various time points and the 55Fe amounts in biotinylated and non-biotinylated fractions were counted. Data shown are means and standard deviations for triplicate replication of the experiment. The experiment was performed in triplicate.
Mentions: Degradation of biotinylated ferritin consisted of two phases with different degradation time constants (Figure 6). Phase one was for the first 4 h and phase two was for the remaining experimental period. In phases one and two, the concentration of biotinylated ferritin decreased with rates of about 20% per h and 1–2% per h, respectively. Possibly because biotinylated ferritin stayed within endosomes for approximately 2 h within phase one, it decreased faster due to the lower pH of endosome, which facilitates the ferritin degradation process in phase one. This indicates that not all of the exogenous ferritin degrades at the end of endosome (within the 2 h period) and the remaining ferritin continues degrading at a slower rate in the intracellular environment.

Bottom Line: At the end of endocytosis, about 28% HFt remained intact and the rest was degraded.Iron released from degraded HFt was in the labile iron pool (LIP) and stimulated the generation of endogenous HFt for new storage.Both experimental data and the model showed that TIM-2 was not involved in the process of iron export.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, North Carolina Agricultural and Technical State University Greensboro, NC, USA.

ABSTRACT
Circuit simulation is a powerful methodology to generate differential mathematical models. Due to its highly accurate modeling capability, circuit simulation can be used to investigate interactions between the parts and processes of a cellular system. Circuit simulation has become a core technology for the field of electrical engineering, but its application in biology has not yet been fully realized. As a case study for evaluating the more advanced features of a circuit simulation tool called Advanced Design System (ADS), we collected and modeled laboratory data for iron metabolism in mouse kidney cells for a H ferritin (HFt) receptor, T cell immunoglobulin and mucin domain-2 (TIM-2). The internal controlling parameters of TIM-2 associated iron metabolism were extracted and the ratios of iron movement among cellular compartments were quantified by ADS. The differential model processed by circuit simulation demonstrated a capability to identify variables and predict outcomes that could not be readily measured by in vitro experiments. For example, an initial rate of uptake of iron-loaded HFt (Fe-HFt) was 2.17 pmol per million cells. TIM-2 binding probability with Fe-HFt was 16.6%. An average of 8.5 min was required for the complex of TIM-2 and Fe-HFt to form an endosome. The endosome containing HFt lasted roughly 2 h. At the end of endocytosis, about 28% HFt remained intact and the rest was degraded. Iron released from degraded HFt was in the labile iron pool (LIP) and stimulated the generation of endogenous HFt for new storage. Both experimental data and the model showed that TIM-2 was not involved in the process of iron export. The extracted internal controlling parameters successfully captured the complexity of TIM-2 pathway and the use of circuit simulation-based modeling across a wider range of cellular systems is the next step for validating the significance and utility of this method.

No MeSH data available.