Ryanodine receptor cluster remodeling links COL4A2 mutation to cerebral artery dysfunction

Pathogenic variants of COL4A1 and COL4A2, which encode the 1 and 2 chains of type IV collagen in vascular basement membranes, cause cerebral small vessel disease and intracerebral hemorrhage, but the signaling mechanisms that precede vascular damage remain incompletely defined. Here, we investigated cerebral arterial function in mice heterozygous for the Col4a2+/G646D mutation. Cerebral pial arteries from aged (12-month-old), but not young (3-month-old), Col4a2+/G646D mice exhibited impaired pressure-induced myogenic tone, whereas downstream parenchymal arterioles retained normal myogenic responsiveness, revealing a segment-selective vascular defect. The frequency of subcellular Ca2+ signals (Ca2+ sparks) generated by the release of Ca2+ through ryanodine receptors (RyR2s) on the sarcoplasmic reticulum (SR) was increased, and large-conductance Ca2+-activated K+ (BK) channel activity was elevated, in cerebral pial artery smooth muscle cells (SMCs) from aged Col4a2+/G646D mice. SR Ca2+ store load and Ryr2 transcript abundance were unchanged in these cells, but Stimulated Emission Depletion super-resolution microscopy revealed that RyR2 protein clusters were enlarged compared with controls. Protein kinase A (PKA) activation reproduced RyR2 cluster enlargement, whereas PKA inhibition normalized RyR2 cluster organization and BK channel activity in SMCs from aged Col4a2+/G646D mice. These findings identify age-associated, PKA-dependent, nanoscale remodeling of RyR2 clusters as a previously unknown mechanism underlying cerebral arterial dysfunction in COL4A2-related disease.