Proinsulin C-peptide and its analogues induce intracellular Ca2+ increases in human renal tubular cells.
Based on the findings that proinsulin C-peptide binds specifically to cell membranes, we investigated the effects of C-peptide and related molecules on the intracellular Ca2+ concentration ([Ca2+]i) in human renal tubular cells using the indicator fura-2/AM. The results show that human C-peptide and its C-terminal pentapeptide (positions 27-31, EGSLQ), but not the des (27-31) C-peptide or randomly scrambled C-peptide, elicit a transient increase in [Ca2+]i. Rat C-peptide and rat C-terminal pentapeptide also induce a [Ca2+]i response in human tubular cells, while a human pentapeptide analogue with Ala at position 1 gives no [Ca2+]i response, and those with Ala at positions 2-5 induce responses with different amplitudes. These results define a species cross-reactivity for C-peptide and demonstrate the importance of Glu at position 1 of the pentapeptide. Preincubation of cells with pertussis toxin abolishes the effect on [Ca2+]i by both C-peptide and the pentapeptide. These results are compatible with previous data on C-peptide binding to cells and activation of Na-,K+ATPase. Combined, all data show that C-peptide is a bioactive peptide and suggest that it elicits changes in [Ca2+]i via G-protein-coupled pathways, giving downstream enzyme effects.
Shafqat
J
J
Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
Juntti-Berggren
L
L
Zhong
Z
Z
Ekberg
K
K
Köhler
M
M
Berggren
P O
PO
Johansson
J
J
Wahren
J
J
Jörnvall
H
H
D000818:Animals; D002096:C-Peptide / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D007684:Kidney Tubules / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D051381:Rats; D013045:Species Specificity
D002096:C-Peptide; D002118:Calcium