Cerebral small vessel diseases (cSVDs) encompass familial and sporadic disorders that affect cerebral arteries, arterioles, capillaries, and venules. Gould syndrome, a monogenic cSVD caused by autosomal-dominant mutations in COL4A1 or COL4A2, is characterized by white matter hyperintensities, microbleeds, and intracerebral hemorrhage (ICH). Impaired-pressure-induced vasoconstriction, an essential autoregulatory response, is linked to age-dependent ICH in Col4a1 mutant mice, but the mechanisms underlying vascular dysfunction in Col4a2 mutants remain poorly understood. Here, we examined a pathogenic Col4a2 missense mutation that replaces glycine 646 with aspartate (Col4a2G646D). Pressure-induced vasoconstriction of cerebral pial arteries from one-year-old Col4a2+/G646D mice was significantly reduced compared to controls. Activation of large-conductance Ca 2+ -activated K + (BK) channels in cerebral artery smooth muscle cells (SMCs) hyperpolarizes the membrane potential and directly counteracts the depolarization that drives pressure-induced vasoconstriction. To test whether BK channels are linked to impaired-pressure-induced vasoconstriction in Col4a2+/G646D mice, we performed patch-clamp electrophysiology using native cerebral artery SMCs. We found that transient BK channel current frequency was significantly increased in SMCs from Col4a2+/G646D mice compared with controls. Transient BK currents are triggered by subcellular Ca 2+ signals (“Ca 2+ sparks”) originating from Ca 2+ release from the sarcoplasmic reticulum through ryanodine receptors (RyR). High-speed confocal Ca 2+ imaging showed that Ca 2+ sparks in SMCs from Col4a2+/G646D mice exhibited elevated frequency and a larger spatial spread. Preliminary super-resolution imaging indicated that RyR cluster density is greater in SMCs from Col4a2+/G646D compared with control mice, dynamic predicted by computational modeling to increase Ca 2+ spark frequency. Prior studies suggest that RyR clustering can be regulated by Protein Kinase A (PKA)-dependent phosphorylation. We found that treatment with the selective PKA inhibitor PKI restored pressure-induced contractility in cerebral arteries from Col4a2+/G646D mice. These findings suggest that cerebrovascular dysfunction in Col4a2+/G646D mice results from increased PKA-dependent phosphorylation of RyRs, leading to increased cluster density, elevated Ca 2+ spark frequency, and enhanced BK channel activity that ultimately impairs pressure-induced constriction. Support or Funding Information: R35HL155008 (to SE) and 1RF1NS110044 (to DG and SE). This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Lavanderos et al. (Fri,) studied this question.