Question

PLEASE ANSWER ALL PARTS

Chapter 7

You have a patient that exhibits the beginning symptoms of neurological loss of function and decide to sequence the patient’s genome to characterize any genetic markers for disease. You notice a mutation in prion (PrP) protein’s GPI anchor domain.

A. Describe what mutations would likely cause loss of function (in relation to the GPI anchor and the PTMs of PrP).

B. Describe how you would characterize any problems in the patient’s carbohydrate using biochemistry-based assays.

C. You decide to study the patient’s PrP function in vitro and in vivo. Describe ways you could do that.

D. Propose a function for the octapeptide repeat in PrP.

Answer 1

A)  PrP potently inhibits Bax-induced cell death in human primary neurons. Deletion of four octapeptide repeats of PrP (PrPOR) and familial D178N and T183A PrP mutations completely or partially eliminate the neuroprotective effect of PrP. PrP remains anti-apoptotic despite truncation of the glycosylphosphatidylinositol (GPI) anchor signal peptide, indicating that the neuroprotective form of PrP does not require the abundant cell surface GPI-anchored PrP.

B) Clinical biochemistry refers to the analysis of the blood plasma (or serum) for a wide variety of substances, substrates, enzymes, hormones, etc and their use in diagnosis and monitoring of disease. Analysis of other body fluids (eg, urine, ascitic fluids, CSF) is also included. Glucose level increases due to high-carbohydrate meals, sprint exercise, stress or excitement (including handling and sampling stress), glucocorticoid therapy, hyperadrenocorticism, overinfusion with glucose/dextrose-containing IV fluids, and diabetes mellitus. It decreases due to insulin overdose, insulinoma, islet cell hyperplasia (uncommon), acetonemia/pregnancy toxemia, acute febrile illness, and idiopathically.

D) The abundant glycine in the octapeptide PrP mammalian repeat avoids steric hinderance. For mammalian genetics, the issue is the DNA's high GC content and apparently consequent slipping and back-hybridizing of newly synthesized DNA during replication, which results in a wide varity of CJD-causing repeat insertions and deletions