Caloxins: a novel class of selective plasma membrane Ca2+ pump inhibitors obtained using biotechnology

  • Magdalena M. Szewczyk
  • Jyoti Pande
  • Ashok K. Grover
Invited Review

DOI: 10.1007/s00424-007-0348-6

Cite this article as:
Szewczyk, M.M., Pande, J. & Grover, A.K. Pflugers Arch - Eur J Physiol (2008) 456: 255. doi:10.1007/s00424-007-0348-6


Plasma membrane Ca2+ pumps (PMCA) extrude cellular Ca2+ with a high affinity and hence play a major role in Ca2+ homeostasis and signaling. Caloxins (selective extracellular PMCA inhibitors) would aid in elucidating the physiology of PMCA. PMCA proteins have five extracellular domains (exdoms). Our hypotheses are: 1) peptides that bind selectively to each exdom can be invented by screening a random peptide library, and 2) a peptide can modulate PMCA activity by binding to one of the exdoms. The first caloxin 2a1, selected for binding exdom 2 was selective for PMCA (Ki = 529 μM). It has been used to examine the physiological role of PMCA. PMCA isoforms are encoded by four genes. PMCA isoform expression differs in various cell types, with PMCA1 and 4 being the most widely distributed. There are differences between PMCA1-4 exdom 1 sequences, which may be exploited for inventing isoform selective caloxins. Using exdom 1 of PMCA4 as a target, modified screening procedures and mutagenesis led to the high-affinity caloxin 1c2 (Ki = 2.3 μM for PMCA4). It is selective for PMCA4 over PMCA1, 2, or 3. We hope that caloxins can be used to discern the roles of individual PMCA isoforms in Ca2+ homeostasis and signaling. Caloxins may also become clinically useful in cardiovascular diseases, neurological disorders, retinopathy, cancer, and contraception.


Phage display Calcium signaling PMCA Hypertension Neuronal disorders Contraception Caveolae Lipid rafts 



cytosolic [Ca2+]


extracellular domain


neuronal nitric oxide synthase


Na+-Ca2+ exchanger


plasma membrane


plasma membrane Ca2+ pump


sarco/endoplasmic reticulum Ca2+ pump

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Magdalena M. Szewczyk
    • 2
  • Jyoti Pande
    • 2
  • Ashok K. Grover
    • 1
    • 2
  1. 1.Department of MedicineMcMaster UniversityHamiltonCanada
  2. 2.Department of BiologyMcMaster UniversityHamiltonCanada

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