**Question:** All of the following have receptors which are transcription factors except

A. Nuclear Factor Kappa-B (NF-κB)
B. G Protein-Coupled Receptors (GPCRs)
C. Epinephrine Receptors (adrenergic receptors)
D. Glucagon Receptors

**Core Concept:** Transcription factors are proteins that regulate gene expression by binding to specific DNA sequences within the promoter or enhancer regions of a gene. When activated by their respective ligands, transcription factors can initiate or inhibit the transcription process, ultimately affecting the synthesis of proteins within the cell.

**Why the Correct Answer is Right:** Glucagon receptors and epinephrine receptors (adrenergic receptors) are classified as **G Protein-Coupled Receptors (GPCRs)**. GPCRs are membrane-bound proteins that transmit signals across the cell membrane, regulating various physiological processes. Unlike GPCRs, transcription factors are intracellular proteins that control gene expression by binding to DNA sequences.

**Why Each Wrong Option is Incorrect:**

A. Nuclear Factor Kappa-B (NF-κB) is a transcription factor that plays a crucial role in immune response, inflammation, and cell survival. It is involved in regulating gene expression and is not a GPCR.

B. Epinephrine receptors (adrenergic receptors) are GPCRs that respond to catecholamines like epinephrine and norepinephrine. They mediate the effects of these hormones on various physiological processes.

C. Glucagon receptors are also GPCRs, activated by the hormone glucagon, and are involved in regulating glucose homeostasis. They function as GPCRs and not transcription factors.

D. Glucagon receptors are GPCRs activated by the hormone glucagon and are involved in regulating glucose homeostasis. They function as GPCRs and not transcription factors.

**Clinical Pearl:** The distinction between GPCRs and transcription factors is crucial for understanding cellular signaling pathways and the regulation of gene expression in various physiological processes. Knowledge of these differences helps in interpreting experimental findings and understanding disease mechanisms involving GPCRs and transcription factors.