BI301 - Lymphocyte Receptor Signaling

Antigen receptors bear intrinsic kinase activity that allows for phosphorylation of cytoplasmic proteins and subsequent downstream signaling events.

False

Which of the following alterations would result in increased activity of Ras (one or more may apply):

A. A mutation in Ras that enhances its GTpase activity
B. Overexpression of GEFs
C. Depletion of GTP in the cytoplasm
D. Overexpression of GAPs
E. A mutation in Ras that renders it unsusceptible to the activities of GAPs

B. Overexpression of GEFs

E. A mutation in Ras that renders it unsusceptible to the activities of GAPs

Which of the follow statements is false?

A. K63 polyubiquitination leads to downstream cellular signaling.
B. K48 polyubiquitination leads to degradation by the proteasome.
C. out of the three families of enzymes involved in ubiquitination—e1 (ubiquitin-activating) enzymes, e2 (ubiquitin-conjugating) enzymes, and e3 enzymes (ubiquitin ligases)—cbl is an e3 enzyme that selects its target via its Sh2 domain.
D. mono- or di-ubiquitination of surface receptors leads to degradation by the proteasome.

D. mono- or di-ubiquitination of surface receptors leads to degradation by the proteasome.

CTLA-4 and PD-1 are both ITIM-containing inhibitory receptors that interfere with co-stimulatory signaling pathways by activating intracellular protein and/or lipid phosphatases.

False

Intravenous administration of exogenous immunoglobulin is a widely used therapy for autoimmune disorders that involve the production of autoantibodies (antibodies against self antigens). Researchers have discovered that the presence of sialic acids on the infused immunoglobulins is critical for the inhibition of autoantibody production in the patient’s own B cells. Which of the following receptors could potentially be responsible for the inhibition of antibody production by B cells, given this finding?

A. FcγRIIB
B. CD22
C. PD-1
D. CD40
E. BTLA

B. CD22