Ca 2+ homeostasis in microvascular endothelial cells from an insulin dependent diabetic model: role of endosomes/Lysosomes

Shankar C. Sanka, David C. Bennett, Jose Rojas, Geraldine B. Tasby, Cynthia J. Meininger, Guoyao Wu, Donald E. Wesson, Curt Pfarr, Raul Martinez-Zaguilan

Research output: Chapter in Book/Report/Conference proceedingChapter

1 Scopus citations

Abstract

Cytosolic Ca 2+ ([Ca 2+] cyt) regulates several functions, e.g. cell growth, contraction, secretion, etc. In many cell types, ion homeostasis appears to be coupled with glucose metabolism. In certain cell types, a strict coupling between glycolysis and the activity of Sarcoplasmic/Endoplasmic Reticulum Ca 2+-ATPases (SERCA) has been suggested. Glucose metabolism is altered in diabetes. We hypothesize that: (a) Ca 2+ homeostasis is altered in microvascular endothelial cells from diabetic animals due to the dysfunction of glycolysis coupling the activity of SERCA; (b) endosomal/lysosomal (E/L) compartments expressing SERCA are involved in the dysfunction associated with diabetes. Ca 2+ ions in E/L compartments can be studied by either spectral imaging/confocal microscopy in single cells, or by fluorescence spectroscopy in cell populations. In cell populations, agonist stimulation elicited greater [Ca 2+] cyt increases in cells from diabetic than from normal animals. Simultaneous measurements of [Ca 2+] cyt and Ca 2+ in E/L compartments ([Ca 2+] E/L) using fluorescence spectroscopy and spectral imaging/confocal microscopy, demonstrate that Ca 2+ is released from E/L compartments following agonist stimulation. Immunocytochemical studies demonstrate that E/L compartments exhibit the machinery to regulate Ca 2+: SERCA and ryanodine receptor (RyR) coupled Ca 2+ channels. Our functional studies, using confocal/spectral imaging microscopy, indicated that E/L compartments employ SERCA and RyR coupled Ca 2+ channels to refill and release Ca 2+, respectively. Glucose modulates refilling of E/L compartments with Ca 2+ via SERCA, since SERCA inhibitors suppress this refilling. The regulation of these phenomena are altered in diabetes. These data indicate that E/L compartments are important for Ca 2+ homeostasis.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
PublisherSPIE
Pages56-66
Number of pages11
Volume3924
StatePublished - 2000
Externally publishedYes
EventMolecular Imaging: Reporters, Dyes, Markers, and Instrumentation - San Jose, CA, USA
Duration: Jan 23 2000Jan 24 2000

Other

OtherMolecular Imaging: Reporters, Dyes, Markers, and Instrumentation
CitySan Jose, CA, USA
Period1/23/001/24/00

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ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics

Cite this

Sanka, S. C., Bennett, D. C., Rojas, J., Tasby, G. B., Meininger, C. J., Wu, G., Wesson, D. E., Pfarr, C., & Martinez-Zaguilan, R. (2000). Ca 2+ homeostasis in microvascular endothelial cells from an insulin dependent diabetic model: role of endosomes/Lysosomes. In Proceedings of SPIE - The International Society for Optical Engineering (Vol. 3924, pp. 56-66). SPIE.