Figure legends
Figure 1. Schematic
showing GPCR signaling and functions in the epididymis and efferent
ductules.
Above: The efferent ductules are a series of tubules that connect the
rete testis to the epididymis. The epithelia of the efferent ductules
are mainly composed of two cell types, ciliated cells and non-ciliated
cells. The
epididymis
is composed of one highly convoluted tubule. The epididymis is segmented
morphologically and functionally into following distinct regions: the
initial segment (not existing in human epididymis), the caput, the
corpus, and the cauda. Each part consists of several cell types,
including principal cells, narrow cells, clear cells, and basal cells.
Inset: G protein-coupled estrogen receptor 1 (GPER) activates
cAMP-CFTR-chloride transportation to maintain the osmotic pressure of
the perfusion solution. ADGRG2 is located exclusively on the apical
membrane in non-ciliated cells. ADGRG2/β-arrestin-1/Gq/CFTR forms a
supercomplex that maintains pH and chloride anion homeostasis. AGTR2 is
specifically detected in basal cells and is essential for the
proton-secretion function of the epididymal lumen through activation of
the nitric oxide (NO)-cGMP pathway. Different members of the adenosine
receptor family have opposite effects on the contractility of the
epididymis. LGR4 activates Gs to increase intracellular cAMP levels,
which promote ERα expression.
Figure
2. GPCR mutations associated with disease.
Schematic representation of the structures of ADGRG2 (A), AGTR2 (B), and
LGR4 (C). The approximate positions of different mutations are
indicated. Abbreviations: PLL domain,
pentraxin/laminin/neurexin/sex-hormone-binding-globulin-like domain;
GPS, G protein-coupled receptor proteolytic site; LRR, leucine-rich
repeats.
Tables
Table 1. GPCRs with known functions in epididymis or efferent ductules