Journal
AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY
Volume 292, Issue 6, Pages C2084-C2094Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpcell.00523.2006
Keywords
sarco(endo)plasmic reticulum calcium-adenosine triphosphatase; differentiation; C2C12 myocytes; vesicle trafficking
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Funding
- NHLBI NIH HHS [HL-064031] Funding Source: Medline
- NINDS NIH HHS [NS-23868] Funding Source: Medline
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Phospholamban (PLB) associates with the Ca2+-ATPase in sarcoplasmic reticulum (SR) membranes to permit the modulation of contraction in response to beta-adrenergic signaling. To understand how coordinated changes in the abundance and intracellular trafficking of PLB and the Ca2+-ATPase contribute to the maturation of functional muscle, we measured changes in abundance, location, and turnover of endogenous and tagged proteins in myoblasts and during their differentiation. We found that PLB is constitutively expressed in both myoblasts and differentiated myotubes, whereas abundance increases of the Ca2+-ATPase coincide with the formation of differentiated myotubes. We observed that PLB is primarily present in highly mobile vesicular structures outside the endoplasmic reticulum, irrespective of the expression of the Ca2+-ATPase, indicating that PLB targeting is regulated through vesicle trafficking. Moreover, using pulse-chase methods, we observed that in myoblasts, PLB is trafficked through directed transport through the Golgi to the plasma membrane before endosome-mediated internalization. The observed trafficking of PLB to the plasma membrane suggests an important role for PLB during muscle differentiation, which is distinct from its previously recognized role in the regulation of the Ca2+-ATPase.
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