PA1b, a plant peptide, induces intracellular [Ca2+] increase via Ca2+ influx through the L-type Ca2+ channel and triggers secretion in pancreatic beta cells.
Using alginic acid to adsorb polypeptides at pH 2.7, we isolated a peptide pea albumin 1b (PA1b) from pea seeds. The PA1b is a single chain peptide consisting of 37 amino acid residues with 6 cysteines which constitutes the cystine-knot structure. Using microfluorometry and patch clamp techniques, we found that PA1b significantly elevated the intracellular calcium level ([Ca2+]i) and elicited membrane capacitance increase in the primary rat pancreatic beta cells. The PA1b effect on [Ca2+]i elevation was abolished in the absence of extracellular Ca2+ or in the presence of L-type Ca2+ channel blocker, nimodipine. Interestingly, we found that PA1b significantly depolarized membrane potential, which could lead to the opening of voltage-dependent L-type Ca2+ channels and influx of extracellular Ca2+, and then evoke robust secretion. In this study we identified the plant peptide PA1b which is capable of affecting the excitability and function of mammalian pancreatic beta cell.
Hu
ZhiTao
Z
Joint Laboratory of Institute of Biophysics and Huazhong University of Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, China.
Dun
XinPeng
X
Zhang
Ming
M
Zhu
HongLiang
H
Xie
Li
L
Wu
ZhengXing
Z
Chen
ZhengWang
Z
Xu
Tao
T
D000464:Alginates; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000502:physiology*; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D006863:Hydrogen-Ion Concentration; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D008297:Male; D008969:Molecular Sequence Data; D018532:Pisum sativum; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D010940:Plant Proteins / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012639:Seeds; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D000464:Alginates; D020746:Calcium Channels, L-Type; D006603:Hexuronic Acids; D010446:Peptide Fragments; D010940:Plant Proteins; D020723:Glucuronic Acid; D002118:Calcium