High impact information on END3

• Normal actin cytoskeleton organization in budding yeast requires the function of the Pan1p/ End3p complex [1].
• Vacuolar localization of ALP in these mutants does not require transport to the plasma membrane followed by endocytic uptake, as double mutants of pep12tsf and vps45tsf with sec1 and end3 sort and mature ALP at the non-permissive temperature [2].
• Like intact Ste2p, the chimeric protein, Stex22p, undergoes rapid endocytosis that is dependent on clathrin and End3p [3].
• END3 and END4 are the first genes shown to be necessary for the internalization step of receptor-borne and fluid-phase markers in yeast [4].
• Here we show that the stabilization of the actin cytoskeleton caused by deletion of Sla1p or End3p leads to hyperactivation of the Ras signaling pathway [5].

Biological context of END3

• The iron deficiency of atx1 mutants is augmented by mutations in END3 blocking endocytosis, suggesting that a parallel pathway for intracellular copper trafficking is mediated by endocytosis [6].
• The END3 gene product is a 40-kDa protein that has a putative EF-hand Ca(2+)-binding site, a consensus sequence for the binding of phosphotidylinositol 4,5-bisphosphate (PIP2), and a C-terminal domain containing two homologous regions of 17-19 aa [7].
• The END3 gene was cloned by complementation of the temperature-sensitive growth defect caused by the end3 mutation and the END3 nucleotide sequence was determined [7].
• Interestingly, while the MKT1 and END3 coding polymorphisms contribute to phenotype, it is the RHO2 3'UTR polymorphisms that are phenotypically relevant [8].
• In vitro phosphorylation assays demonstrate that Prk1p is able to phosphorylate regions of Pan1p containing the LxxQxTG repeats, including the region responsible for binding to End3p [1].

Anatomical context of END3

• The END3 gene encodes a protein that is required for the internalization step of endocytosis and for actin cytoskeleton organization in yeast [7].
• Degradation depended on delivery of the permease to the vacuole through the END3/END4 endocytic pathway [9].
• These cell wall defects are also exhibited by wild-type cells overproducing the C-terminal region of Sla1p that is responsible for interactions with Pan1p and End3p [10].
• We show that cells expressing a mutated form of Sla1p or lacking End3p display markers of apoptosis such as depolarized mitochondrial membranes and elevated levels of reactive oxygen species [11].

Associations of END3 with chemical compounds

• Since the end3/end4 mutations did not affect uptake activity under derepressed conditions, endocytosis is not required for normal inositol uptake [12].
• Disruption of END3, a gene required for an early step of endocytosis, increased the abundance of Agp2p, an effect that was paralleled by a marked up-regulation of spermidine transport velocity [13].
• Second, its NH2 terminus shows significant homology to the NH2 terminus of yeast End3p, necessary for endocytosis of alpha-factor [14].

Physical interactions of END3

• EH domain proteins Pan1p and End3p are components of a complex that plays a dual role in organization of the cortical actin cytoskeleton and endocytosis in Saccharomyces cerevisiae [15].

Co-localisations of END3

• End3p-GFP localized to cell and spore peripheries in vegetative and sporulating cells and colocalized with actin structures [16].

Other interactions of END3

• Degradation was not observed in strains defective in the END3/END4 endocytic pathway or in the production of vacuolar proteases (PEP4) [12].
• Using strains carrying mutations in END3, REN1(VPS2), PEP4, and PRE1 PRE2, we demonstrate that the proteolysis of Mal61/HAp is dependent on endocytosis and vacuolar proteolysis and is independent of the proteosome [17].
• In addition, when vps8 mutants are combined with endocytic or late secretory pathway mutants (end3 or sec1, respectively), ALP is still delivered to the vacuole [18].
• Localisation of Sla1p at the cell cortex is, however, dependent on the EH-domain-containing protein End3p, which is part of the yeast endocytic machinery [19].
• Using well characterized npi1 and end3 mutants deficient in the endocytic pathway, we demonstrate that Alr1 protein turnover is dependent on ubiquitination and endocytosis [20].

References