Vesicular Traffic and Protein Quality Control

Flashcards covering key vocabulary related to vesicular traffic, protein quality control in the ER, and related cellular pathways and diseases.

ER Lumen

The primary organelle for protein processes and modifications, including folding and glycosylation.

Chaperone proteins

Proteins that assist in the proper folding of other polypeptides into their correct shapes.

BiP (Binding Immunoglobin Protein)

A chaperone protein belonging to the HSP family, found in the ER, which aids in protein folding and assembly and is important for the Unfolded-Protein Response.

Unfolded-Protein Response (UPR)

A cellular protective mechanism triggered by the accumulation of unfolded or misfolded proteins in the ER, leading to pathways like Ire1, ATF6, and PERK.

Glycosylation

The process of adding oligosaccharides to polypeptides to form glycoproteins, performed by glycosyltransferases inside the ER lumen.

Glycosyltransferases (GTs)

Enzymes responsible for building and attaching oligosaccharides to polypeptides in the ER lumen to form glycoproteins.

Protein disulfide isomerase (PDI)

An enzyme that forms or transfers disulfide bonds within polypeptides, helping to stabilize protein folding.

Signal cleavage

The removal of an N-terminal signal sequence from a polypeptide, a modification that occurs in the ER lumen.

Fluorescent tags

A method considered most effective for tracking protein movement through cells.

GTPase

A protein that provides energy for the interaction with cargo during vesicle formation by swapping GDP for GTP, with different types used in different cell locations.

Dynamin

A protein responsible for stretching and pinching the neck of a budding vesicle, providing energy to cut it from the parent membrane.

GTP hydrolysis

The process that uses GTP as an energy source to free a vesicle from its parent membrane and disassemble its protein coat.

Protein coat

A layer of proteins that forms on the cytosolic side of a membrane, giving shape to a vesicle and helping it localize to a particular organelle.

COPI vesicles

Vesicles involved in retrograde transportation (e.g., from Golgi to ER), characterized by coat proteins (COPs) and utilizing ARF as a GTPase.

COPII vesicles

Vesicles involved in anterograde transportation (e.g., from ER to Golgi), characterized by Sec (secretion) proteins as coat proteins and utilizing Sar1 as a GTPase.

Clathrin-coated vesicles

Vesicles prevalent in various transport routes (e.g., from cell membrane, to lysosomes, peroxisomes), characterized by clathrin coat proteins and utilizing ARF as a GTPase.

Receptor-mediated endocytosis of LDL particles

A cellular process where LDL particles, containing cholesterol, are taken into the cell via clathrin-coated vesicles after binding to specific receptors.

LDL particle

A lipoprotein complex containing cholesterol in a tight ball, surrounded by a single phospholipid layer and a protein band that acts as a tag for cellular entry.

Ire1 Pathway

A branch of the Unfolded-Protein Response where accumulation of unfolded proteins causes BiP to diffuse away from IRE sensors, leading IRE1 to signal for more chaperone proteins and folding.

ATF6 Pathway

A branch of the Unfolded-Protein Response where ATF6 is spliced in the Golgi, and the newly spliced protein acts as a transcription factor for the ERAD pathway.

ERAD pathway

Endoplasmic Reticulum-Associated Degradation pathway, which finds unfolded proteins in the ER, extracts them into the cytosol, and degrades them via proteasomes.

PERK Pathway

A branch of the Unfolded-Protein Response that inhibits transcription and translation by signaling the production of Eif2, activated when BiP diffuses away from PERK to bind unfolded proteins.

Huntington’s Disease

A neurodegenerative disorder caused by a mutation in the huntingtin protein (HTT) leading to the accumulation of excessively long glutamine chains in the ER, triggering the UPR and excessive neuronal stimulation due to calcium release.

Membrane cholesterol

A component of cell membranes that influences LDL endocytosis; higher levels in the membrane lead to less LDL binding to its receptor and thus less endocytosis.