Molecular insights into SERCA regulation by endogenous peptide modulators

• Author / Creator

  Gorski, Przemyslaw A

• In human cells, oscillations in calcium concentration serve as a mechanism for controlling a variety of physiological processes including muscle contraction and relaxation. The sarcoplasmic reticulum (SR) is a calcium storage organelle in muscle cells that contains a calcium pump (SERCA) required for the reuptake of calcium into the SR for muscle relaxation. The activity of SERCA is tightly regulated through reversible interactions with the short integral membrane proteins, phospholamban (PLN) and sarcolipin (SLN). Defects in the regulation of SERCA are a central determinant in end-stage heart failure. Consequently, the regulatory mechanisms imposed by PLN and SLN could have clinical implications for heart and skeletal muscle diseases. This thesis aims to provide functional insights into regulatory complexes formed between SERCA and its endogenous peptide modulators.
  We sought to examine how SERCA activity is regulated by tissue-specific endogenous peptide modulators in order to meet the physiological needs of a specific cell type. Using alanine-scanning mutagenesis and chimeric PLN-SLN constructs, we identified the highly conserved luminal extension of SLN as a functionally important and transferrable domain that is a primary determinant for SERCA inhibition. Based on these findings, we concluded that SLN uses an inhibitory mechanism that is distinct from that of PLN. We also studied the ability of zebrafish phospholamban-like protein (zfPLN) to regulate SERCA. Functional analysis of zfPLN revealed that despite the high sequence diversity between zebrafish and human PLN, as well as the presence of a unique zfPLN luminal extension, zfPLN has inhibitory properties that are similar to human PLN. Finally, we examined the role of the 11th transmembrane segment (TM11) of the ubiquitous SERCA2b in calcium transport. Our studies revealed that TM11 is a distinct and highly conserved functional region of SERCA2b that serves as a genuine regulator of the calcium pump. Combined, the results provide novel insights into the different mechanisms of SERCA regulation by endogenous peptide modulators.

• Subjects / Keywords

  • Phospholamban
  • Sarcolipin
  • SERCA

• Graduation date

  Fall 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3S756S22

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.