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Abstract
The Saccharomyces cerevisiae plasma membrane has been proposed to contain two stably distributed domains. One of these domains, known as MCC (membrane compartment of Can1) or eisosomes, consists of furrow-like membrane invaginations and associated proteins. The other domain, called MCP (membrane compartment of Pma1), consists of the rest of the membrane area surrounding the MCC patches. The role of this plasma membrane domain organization in endocytosis is under debate. Here we show by live-cell imaging that vesicular traffic is restricted to the MCP and the distribution of endocytic and exocytic sites within the MCP is independent of the MCC patch positions. Photobleaching experiments indicated that Can1 and Tat2, two MCC-enriched permeases, exchange quickly between the two domains. Total internal reflection fluorescence and epi-fluorescence microscopy showed that the enrichment of Can1 at the MCC persisted after addition of its substrate, whereas the enrichment of Tat2 disappeared within 90 seconds. The rates of stimulated endocytosis of Can1 as well as Tat2 were similar in both wild-type cells and pil1Δ cells, which lack the MCC. Thus, our data suggest that the enrichment of certain plasma membrane proteins in the MCC does not regulate the rate of their endocytosis.
Highlights
The yeast plasma membrane contains two membrane domains, which have a stable distribution
We show by live-cell imaging that vesicular traffic is restricted to the MCP and the distribution of endocytic and exocytic sites within the MCP is independent of the MCC patch positions
Total internal reflection fluorescence and epi-fluorescence microscopy showed that the enrichment of Can1 at the MCC persisted after addition of its substrate, whereas the enrichment of Tat2 disappeared within 90 seconds
Summary
The yeast plasma membrane contains two membrane domains, which have a stable distribution. A recent electron microscopy study showed that the patches defining the first domain correspond to furrow-like membrane invaginations which are ~300 nm long, ~150–250 nm deep and ~50 nm wide (Stradalova et al, 2009) This membrane domain has been called eisosomes (Walther et al, 2006) or MCC (membrane compartment of Can1) because the arginine permease Can is enriched in the patches (Grossmann et al, 2007). The H+-ATPase Pma is excluded from the MCC and localizes to the remainder of the plasma membrane surrounding the MCC patches (Malinska et al, 2003) This domain was termed MCP (membrane compartment of Pma1) (Grossmann et al, 2007). The hexose transporter Hxt and the general amino acid permease Gap are evenly distributed to both MCC and MCP domains (Lauwers et al, 2007; Malinska et al, 2003)
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