Limits...
Stringent requirement for HRD1, SEL1L, and OS-9/XTP3-B for disposal of ERAD-LS substrates.

Bernasconi R, Galli C, Calanca V, Nakajima T, Molinari M - J. Cell Biol. (2010)

Bottom Line: The presence of structural lesions in the luminal, transmembrane, or cytosolic domains determines the classification of misfolded polypeptides as ERAD-L, -M, or -C substrates and results in selection of distinct degradation pathways.In this study, we show that disposal of soluble (nontransmembrane) polypeptides with luminal lesions (ERAD-L(S) substrates) is strictly dependent on the E3 ubiquitin ligase HRD1, the associated cargo receptor SEL1L, and two interchangeable ERAD lectins, OS-9 and XTP3-B.Our data reveal that, in contrast to budding yeast, tethering of mammalian ERAD-L substrates to the membrane changes selection of the degradation pathway.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute for Research in Biomedicine, 6500 Bellinzona, Switzerland.

ABSTRACT
Sophisticated quality control mechanisms prolong retention of protein-folding intermediates in the endoplasmic reticulum (ER) until maturation while sorting out terminally misfolded polypeptides for ER-associated degradation (ERAD). The presence of structural lesions in the luminal, transmembrane, or cytosolic domains determines the classification of misfolded polypeptides as ERAD-L, -M, or -C substrates and results in selection of distinct degradation pathways. In this study, we show that disposal of soluble (nontransmembrane) polypeptides with luminal lesions (ERAD-L(S) substrates) is strictly dependent on the E3 ubiquitin ligase HRD1, the associated cargo receptor SEL1L, and two interchangeable ERAD lectins, OS-9 and XTP3-B. These ERAD factors become dispensable for degradation of the same polypeptides when membrane tethered (ERAD-L(M) substrates). Our data reveal that, in contrast to budding yeast, tethering of mammalian ERAD-L substrates to the membrane changes selection of the degradation pathway.

Show MeSH
Schematic representation of the seven canonical ERAD substrates used in this study. BACE476, CD3-δ, NHKBACE, and NHKCD3δ are type I membrane proteins (ERAD-LM substrates); BACE476Δ, CD3-δΔ, and NHK are the corresponding soluble ERAD-LS substrates.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2812524&req=5

fig1: Schematic representation of the seven canonical ERAD substrates used in this study. BACE476, CD3-δ, NHKBACE, and NHKCD3δ are type I membrane proteins (ERAD-LM substrates); BACE476Δ, CD3-δΔ, and NHK are the corresponding soluble ERAD-LS substrates.

Mentions: To better understand this, we compared the requirements for efficient disposal of two canonical, N-glycosylated, membrane-anchored ERAD substrates, BACE476 (Molinari et al., 2002) and CD3-δ (Yang et al., 1998), with the requirements for efficient disposal of their variants lacking the transmembrane anchor (BACE476Δ and CD3-δΔ; Fig. 1). For all of these proteins, extensive demannosylation is required for ERAD. Our data reveal that only degradation of the soluble (nontransmembrane) variants of BACE476 and CD3-δ strictly depend on several participants of the HRD1 pathway regulating ERAD, namely the E3 ubiquitin ligase HRD1, the HRD1-associated cargo receptor SEL1L, and the ERAD lectins OS-9 and XTP3-B. Disposal of the membrane-tethered variants of the same folding-defective polypeptides remained unperturbed upon inactivation of HRD1, SEL1L, and, significantly, OS-9 and XTP3-B. Thus, in contrast to yeast (Quan et al., 2008; Clerc et al., 2009), substrate demannosylation in the mammalian ER is not (only) required to generate a signal for disposal decoded by the ERAD lectins of the OS-9 family. In fact, at least when the folding-defective glycopolypeptide is tethered at the ER membrane, intervention of OS-9 and XTP3-B becomes dispensable for efficient disposal. Moreover, and again in contrast to yeast (Taxis et al.,2003; Willer et al., 2008), the presence or the absence of a membrane anchor alters selection of the disposal pathway used by ERAD-L substrates in mammalian cells. This was confirmed by the finding that the crucial dependency on components of the HRD1 pathway for degradation of NHK, another classical ERAD-L substrate (Liu et al., 1997), was substantially relieved when the protein was anchored at the ER membrane. Our data lead us to group polypeptides with structural lesions in the ER lumen in two subclasses, namely ERAD-LS substrates (for soluble ERAD-L substrates whose disposal is strictly dependent on the HRD1 pathway) and ERAD-LM substrates (for membrane-tethered ERAD-L substrates for which alternative ERAD pathways can be activated to ensure efficient disposal). Our data further highlight the more significant complexity and the somewhat different mechanisms regulating protein quality control in the mammalian versus the budding yeast ER.


Stringent requirement for HRD1, SEL1L, and OS-9/XTP3-B for disposal of ERAD-LS substrates.

Bernasconi R, Galli C, Calanca V, Nakajima T, Molinari M - J. Cell Biol. (2010)

Schematic representation of the seven canonical ERAD substrates used in this study. BACE476, CD3-δ, NHKBACE, and NHKCD3δ are type I membrane proteins (ERAD-LM substrates); BACE476Δ, CD3-δΔ, and NHK are the corresponding soluble ERAD-LS substrates.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2812524&req=5

fig1: Schematic representation of the seven canonical ERAD substrates used in this study. BACE476, CD3-δ, NHKBACE, and NHKCD3δ are type I membrane proteins (ERAD-LM substrates); BACE476Δ, CD3-δΔ, and NHK are the corresponding soluble ERAD-LS substrates.
Mentions: To better understand this, we compared the requirements for efficient disposal of two canonical, N-glycosylated, membrane-anchored ERAD substrates, BACE476 (Molinari et al., 2002) and CD3-δ (Yang et al., 1998), with the requirements for efficient disposal of their variants lacking the transmembrane anchor (BACE476Δ and CD3-δΔ; Fig. 1). For all of these proteins, extensive demannosylation is required for ERAD. Our data reveal that only degradation of the soluble (nontransmembrane) variants of BACE476 and CD3-δ strictly depend on several participants of the HRD1 pathway regulating ERAD, namely the E3 ubiquitin ligase HRD1, the HRD1-associated cargo receptor SEL1L, and the ERAD lectins OS-9 and XTP3-B. Disposal of the membrane-tethered variants of the same folding-defective polypeptides remained unperturbed upon inactivation of HRD1, SEL1L, and, significantly, OS-9 and XTP3-B. Thus, in contrast to yeast (Quan et al., 2008; Clerc et al., 2009), substrate demannosylation in the mammalian ER is not (only) required to generate a signal for disposal decoded by the ERAD lectins of the OS-9 family. In fact, at least when the folding-defective glycopolypeptide is tethered at the ER membrane, intervention of OS-9 and XTP3-B becomes dispensable for efficient disposal. Moreover, and again in contrast to yeast (Taxis et al.,2003; Willer et al., 2008), the presence or the absence of a membrane anchor alters selection of the disposal pathway used by ERAD-L substrates in mammalian cells. This was confirmed by the finding that the crucial dependency on components of the HRD1 pathway for degradation of NHK, another classical ERAD-L substrate (Liu et al., 1997), was substantially relieved when the protein was anchored at the ER membrane. Our data lead us to group polypeptides with structural lesions in the ER lumen in two subclasses, namely ERAD-LS substrates (for soluble ERAD-L substrates whose disposal is strictly dependent on the HRD1 pathway) and ERAD-LM substrates (for membrane-tethered ERAD-L substrates for which alternative ERAD pathways can be activated to ensure efficient disposal). Our data further highlight the more significant complexity and the somewhat different mechanisms regulating protein quality control in the mammalian versus the budding yeast ER.

Bottom Line: The presence of structural lesions in the luminal, transmembrane, or cytosolic domains determines the classification of misfolded polypeptides as ERAD-L, -M, or -C substrates and results in selection of distinct degradation pathways.In this study, we show that disposal of soluble (nontransmembrane) polypeptides with luminal lesions (ERAD-L(S) substrates) is strictly dependent on the E3 ubiquitin ligase HRD1, the associated cargo receptor SEL1L, and two interchangeable ERAD lectins, OS-9 and XTP3-B.Our data reveal that, in contrast to budding yeast, tethering of mammalian ERAD-L substrates to the membrane changes selection of the degradation pathway.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute for Research in Biomedicine, 6500 Bellinzona, Switzerland.

ABSTRACT
Sophisticated quality control mechanisms prolong retention of protein-folding intermediates in the endoplasmic reticulum (ER) until maturation while sorting out terminally misfolded polypeptides for ER-associated degradation (ERAD). The presence of structural lesions in the luminal, transmembrane, or cytosolic domains determines the classification of misfolded polypeptides as ERAD-L, -M, or -C substrates and results in selection of distinct degradation pathways. In this study, we show that disposal of soluble (nontransmembrane) polypeptides with luminal lesions (ERAD-L(S) substrates) is strictly dependent on the E3 ubiquitin ligase HRD1, the associated cargo receptor SEL1L, and two interchangeable ERAD lectins, OS-9 and XTP3-B. These ERAD factors become dispensable for degradation of the same polypeptides when membrane tethered (ERAD-L(M) substrates). Our data reveal that, in contrast to budding yeast, tethering of mammalian ERAD-L substrates to the membrane changes selection of the degradation pathway.

Show MeSH